NEW YORK (Reuters) - U.S. companies' planned layoffs jumped 68 percent in April from the prior month to the highest since September 2006, pointing to further deterioration in the labor market, a report showed on Thursday.

Planned job cuts in U.S. companies totaled 90,015 last month, up from 53,579 in March and up 27 percent from a year earlier, employment consulting firm Challenger, Gray & Christmas Inc. reported.

The April layoffs were the steepest since the 100,315 cuts announced in September 2006.

Most of the announced job cuts came from the financial sector, due to the housing slump and about $300 billion in write-downs on bad mortgages and investments, the firm said.

The financial services industry announced 23,106 cuts in April with almost half of them occurring in a two-day period that saw hefty planned layoffs from Citigroup (C.N: Quote, Profile, Research) and Merrill Lynch (MER.N: Quote, Profile, Research), it said.

The telecommunications sector was second in announced layoffs in April with 8,007, followed closely by 7,954 planned cuts in the transportation industry.

Employers have announced 290,671 jobs to be eliminated in the first four months of 2008, up 9 percent from the 266,658 cuts recorded during the same span in 2007, the firm said.

Going forward, the fallout from record oil prices may result in more layoffs than the housing slump, John A. Challenger, chief executive officer of Challenger, Gray & Christmas.

"The impact of high gasoline prices is rippling through the economy much faster than the housing collapse ever did or will," Challenger said in a statement.

(Reporting by Richard Leong; Editing by Theodore d'Afflisio)

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