On the 14 September 1876, the claims of Venezuela to western Essequibo were again made in a letter that Government sent to the Earl of Derby, then British Secretary of State for Foreign Affairs. These claims were substantially the same as those stated before in 1844.

However, the letter of September 1876, in addition, relied upon the Bull of Pope Alexander VI of 1493 which granted Spain most of the lands in America. Venezuela also alleged that the Catalonian Capuchin missionaries had occupied the district between the Orinoco and Cape Nassau and between the sea and the Caroni River. The letter further quoted from an old treaty (the Cartel of Aranjuez) which was made between Spain and the Netherlands for the mutual surrender of fugitive slaves in their South American territories. According to the first article of this treaty, an agreement was reached for both Governments to recover fugitive slaves in Essequibo, Demerara, Berbice, and Suriname. Venezuela suggested that Essequibo, according to the Cartel, referred to the river.

A perusal of the treaty, both in the French and Spanish texts, however, showed that this suggestion was unfounded and, further, from the documents which were referred to during the negotiations for the treaty, it was clear that the words Essequibo, Demerara, Berbice and Suriname were used throughout as well-known descriptions of the Dutch colonies. It was also clear that Essequibo was the name commonly applied to all Dutch possessions between the Boeraseri River, situated on the east of the Essequibo River, and the Orinoco.

After the British rejected these claims, Venezuela on the 13 February 1877 sent another letter to the British Government suggesting a settlement of the question by the adoption of a conventional line fixed by agreement between the two countries. This proposal was accepted by the British Government.

Subsequently, on the 19 May 1879, Venezuela, in a Note to the British Government, stated that it possessed proof that the Essequibo River was the eastern boundary of Venezuelan Guiana; the Venezuelan Ambassador, at the same time, requested the Government of Great Britain to make a proposal for "a frontier of accommodation".

In reply, the British Government stated the boundary which the British Government was entitled to claim comprised the territory claimed by the Dutch in their protests of 1759 and 1769. It observed that the claim of Venezuela made in 1876 would involve the surrender of a province then inhabited by 40,000 British subjects, and which had been in the uninterrupted possession of Holland (The Netherlands) and Great Britain successively for two centuries. The British Government also expressed its readiness settle the matter by mutual concession.

On the 21 February 1881, in a Note to the British Government, Venezuela proposed a frontier line starting from a point one mile to the north of the Moruka River, drawn from there westward to the 60th meridian and running south along that meridian. This would have granted the Barima District to Venezuela.

Replying on the 15 September 1881, the British Government rejected the boundary line proposed by Venezuela and stated that the right of the British Government to the Barima District could not be questioned. The British Government, in this reply, proposed another line which conceded part of the British claim to the upper Cuyuni and Amakura areas. However, in spite of frequent inquiries by the British Government, no response to this proposal was received from the Venezuelan Government.

In September 1883, the British Government asked the Venezuelan Government to enter into discussions to settle the boundary dispute. However, the latter replied that the country's Constitution prevented the conclusion of Treaties relating to boundaries, for it denied any Power the right of ceding either by exchange or reparation the smallest portion of any territory assumed to constitute a part of the dominions of the Republic of Venezuela. The Venezuelan Government, therefore, proposed the reference of the question to an arbitrator as the only means of settlement.

It appeared to the British Government that the same provision of the Venezuelan Constitution which prevented the solution of the question by means of a Treaty might be invoked as a pretext for not abiding by the Award if it should prove unfavourable to Venezuela. The British Government, therefore, declined the proposal to refer the boundary to arbitration, but expressed the hope that some other means of settlement might be devised.

In October 1884, the Venezuelan Government suggested that since the British Government had declined arbitration on the boundary question, the matter should be referred to a court of law, the members of which should be chosen by both Venezuela and Great Britain.

To this the British replied, in February 1885, that the proposal presented constitutional difficulties which prevented the British Government from agreeing to it. Great Britain declared that it was not prepared to depart from the arrangement proposed by Venezuela in 1877 to have the boundary fixed by mutual accord between the Governments of the two countries.

In 1886, the British Government proposed to Venezuela that the territory lying between the boundary lines respectively suggested by Venezuela and Great Britain in 1881 should be considered as the territory in dispute between the two countries. Within these limits the boundary line should be traced either by an arbitrator or by a joint commission on the basis of an equal division, with due regard being paid to natural boundaries.

This recommendation, however, was not accepted by Venezuela which continued to assert the claim to all territory as far as the Essequibo River despite its proposal in 1881 of a boundary line along 60 degrees West longitude.

In the meanwhile, a series of encroachments by the Venezuelan Government on the territory in dispute, in violation of the Agreement of 1850, had led the British Government to the conclusion that some definite step must be taken for the protection of the rights and interests of British Guiana.

The most serious violation occurred when the Venezuelan Government in 1883 and 1884 issued grants of land and concessions for the purpose of colonisation in the territory between Barima Point, the Moruka, and the source of the Essequibo. As a result, the British authorities sent officers to warn off any persons who should attempt to put these grants and concessions into effect. Two rural constables were commissioned for the Amakura River in March 1885, and a British Post was established there in August 1886.

In October 1886, a notice by the British Government was published in the London Gazette stating that titles issued by the Venezuelan authorities to land within the territory claimed by the British as forming part of British Guiana could not be recognized by the British Government. The notice declared that any person taking possession of, or exercising any right over such land under the Venezuelan titles, would be treated as a trespasser under the laws of British Guiana.

The publication of this notice drew protests from the Venezuelan Government which shortly afterwards announced its intention of erecting a lighthouse on Barima Point, and stated that if Great Britain opposed this step, diplomatic relations would be broken off.

The British Government offered to agree to the establishment of the lighthouse if it received a formal statement that this measure would in no way be held as surrendering the British claim to the territory in dispute.

This offer was, however, rejected. The Venezuelan Government then for the first time denied that the territory between the Orinoco and the Pomeroon could be considered as being in dispute between the two countries; and it demanded the immediate evacuation of this territory (by the British) and the submission of the whole question to arbitration.

After the rejection of the Venezuelan Government's claim and the refusal to comply with its demands for evacuation of the territory, Venezuela accused Great Britain of "acts of spoliation", and, after expelling the British Ambassador in Caracas, diplomatic relations were broken off by Venezuela in February 1887.

During 1890 and 1893, negotiations were instituted by the Venezuelan Government for the renewal of diplomatic relations and a settlement of the boundary dispute. However, they failed to have any successful result because of the persistence of the Venezuelan negotiators in asserting the claim of Venezuela to all territory as far as the Essequibo River.