Widespread disturbances and a general strike followed an attempt by the Government to introduce new labour-relations legislation. 23 October 1963: In an attempt to resolve a political impasse, a proportional representation electoral system was implemented. 14 December 1964: In a general election the PPP won 24 of the 53 seats in the Legislative Assembly, while the PNC won 22 seats and the right-wing The United Front (TUF) obtained seven seats. A coalition Government was formed by the PNC and TUF, with Burnham appointed as premier. December 1965: Antigua, Barbados and British Guiana signed an agreement to establish the Caribbean Free Trade Area (CARIFTA), which entered into effect (with the additional participation of Trinidad and Tobago) on 1 May 1968. 26 May 1966: The colony of British Guiana became an independent State, within the British Commonwealth, and was renamed Guyana. Burnham was appointed the first Prime Minister and the Governor-General was Sir Richard Luyt. 1968: Despite the resignation of TUF ministers within the PNC-TUF coalition before a general election, the PNC obtained the majority of votes and Burnham continued as Prime Minister. 23 February 1970: A new Constitution renamed the country the Co-operative Republic of Guyana. The office of Governor-General was abolished and, in March, Arthur Chung was elected non-executive President. 1973: CARIFTA became CARICOM (the Caribbean Community and Common Market), a grouping primarily of British Commonwealth Caribbean countries. 1973: The PNC was victorious in general elections, although the results of the poll were disputed by the opposition parties. 1974: In the Declaration of Sophia (named after a Georgetown suburb), the PNC committed itself to stronger socialist policies, and announced that government institutions were arms of the party. 1976: Arthur Chung was re-elected non-executive President.