KINGSTON (Reuters) - Jamaica’s opposition narrowly won a general election on Thursday, with its message of deep tax cuts and massive job creation winning over voters weary of years of tough IMF-mandated austerity measures.

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The Jamaican Labour Party (JLP) led by Andrew Holness had won 33 of the 63 seats with almost all votes counted, according to the electoral council website. Prime Minister Portia Simpson-Miller’s party took 30 seats.

The sound of airhorns filled the JLP’s headquarters in Kingston as a jubilant crowd of supporters in the party’s signature green waved flags and partied to dancehall music, including a song called “Bye bye Portia, bye bye”.

“We will grow the Jamaican economy. We will create jobs. We will give you an accountable and responsive government,” said Holness, 43, adding that his government would address a laundry list of issues from water to housing and healthcare.

“Our mission is to move Jamaica from poverty to prosperity,” he said as supporters rang bells, a party symbol.

Simpson-Miller conceded defeat to a crowd of somber voters.

Holness, who is likely to be the Caribbean nation’s next prime minister, has promised to create 250,000 jobs on the island of 2.7 million people and do away with income tax for many wage earners, a move critics say will tear into the budget.

Opinion polls before the election forecast victory for Simpson-Miller after she returned the heavily indebted economy to growth and low inflation.

Despite her People’s National Party’s socialist past, she embraced spending cuts, wage freezes and harsh fiscal discipline as part of a $1.27 billion IMF bailout that has lowered the still daunting debt burden of more than 130 percent of GDP.

Simpson-Miller, 70, is Jamaica’s first female head of state. Inflation hit a 48-year low during her tenure. Falling oil prices freed up government funds in the import-dependent country and the island’s GDP grew 1.3 percent last year, according to the World Bank.

However, unemployment is high at around 13 percent overall, and a whopping 38 percent for the young. While Simpson-Miller is credited with bringing stability, Holness’ optimistic message was more popular in the end.

“The country wanted to exhale,” one Holness supporter told local television, her name drowned out by the celebrations.

Outgoing education minister Ronald Thwaites questioned Holness’ ability to deliver.

“Can those promises be kept? Will they be kept?” Thwaites said in an interview with local television.

Holness criticized the government’s adherence to austerity but refrained from sharp rhetoric against the IMF plan on the campaign trail.

Holness briefly served as prime minister in 2011 after unrest due to a U.S. attempt to extradite drug kingpin Christopher “Dudus” Coke forced his predecessor to resign.