* Five parties unite to challenge ruling PNM party
* Opposition grouping seeks to cut across ethnic lines
* Energy-based economy jolted by global recession
By Linda Hutchinson-Jafar
FYZABAD, Trinidad and Tobago, April 22 (Reuters) - Five opposition parties in Caribbean gas and oil producer Trinidad and Tobago have signed a unity pact that seeks multi-ethnic support to challenge Prime Minister Patrick Manning's ruling People's National Movement (PNM) in May 24 general elections.
The "People's Partnership" -- uniting opposition leader Kamla Persad-Bissessar's United National Congress (UNC) with the Congress of the People (COP) and three other small parties -- was launched late on Wednesday by Persad-Bissessar before thousands of supporters in the southern town of Fyzabad.
"We are now united in a common purpose as we go forward to forge a new day, a brave new world for Trinidad and Tobago," Persad-Bissessar, 58, the opposition's prime ministerial candidate, told supporters who waved flags and banners.
The opposition grouping seeks to cut across the former British colony's main mix of Afro-Trinidadians and Indo-Trinidadians who traditionally vote along ethnic lines. It will also look to capitalize on popular discontent fueled by the impact of the global downturn on the local economy.
The twin-island state, which lies off Venezuela and is known for its Caribbean calypsos, steel bands and annual carnival, is one of the world's top exporters of liquefied natural gas (LNG) and a leading supplier of LNG to the United States. But the energy-dependent economy has been buffeted by the effects of the international recession.
Manning, 64, who has ruled Trinidad and Tobago for 13 of the past 17 years, earlier this month dissolved parliament midway through his administration's five-term term. He comfortably won re-election in a November 2007 vote.
But his ruling party faces opposition accusations of corruption and that it has squandered energy wealth on high-profile international summits instead of concentrating on providing better services and more jobs for ordinary people.
Manning dismissed the challenge of the diverse opposition grouping, saying that political infighting would undermine its ability to deliver on its promises to the electorate.
"They talk unity but they don't stand for the policies of unity ... and if you vote for them, you eat what the devil kneads," he told supporters late on Wednesday.
Analysts said the opposition coalition faced a tough task to form an effective unified force in Trinidad's traditionally fractious and ethnically diverse politics.
"It can only be sustainable if there is an element of trust and compromise and if the public is convinced that they have the credibility and competence to restructure the governance of the country," political analyst Derek Ramsamooj told Reuters.
"We will respect every one of our partners. We must live with unity in diversity," said UNC leader Persad-Bissessar, who served as the country's first female attorney general in 1995.
Besides the COP led by former Central Bank Governor Winston Dookeran, which has support in the large middle class, the unified opposition accord includes the small National Joint Action Committee, the Tobago Organisation of the People and the Movement for Social Justice.
Trinidad and Tobago's central bank says the country's gross domestic product (GDP) contracted by 3.2 percent last year, a much larger decline than the originally forecast 1.5 to 2 percent. It was the country's first annual decline in GDP in 16 years.
In 2008, real GDP grew by 3.5 percent. The central bank is forecasting 2 percent growth this year.
Manning's government and energy experts have expressed concern that a decline in natural gas reserves could threaten future economic growth prospects and the government is seeking investment partners to explore for new energy reserves.
Editing by Pascal Fletcher and Will Dunham