By Simon Challis

LONDON (Reuters) - The pensions lifeboat fund on Friday raised by more than 50 percent a key element of the levy that pension schemes must pay, sparking criticism from the industry.

The Pension Protection Fund (PPF) set the "scaling factor" -- a crucial determinant of how much firms must pay into the fund -- at 3.77 for the 2008-2009 levy year, up from 2.47 percent the previous year.

Set up in 2005 to guard the benefits of members of final-salary pension schemes whose sponsor firms go bust leaving their funds without enough cash, the PPF is funded primarily by levies on companies with solvent pension schemes.

The scaling factor is the multiplier applied by the PPF to each contributing scheme's individual levy, which is based on calculations regarding the risk they pose to the PPF, to meet the total amount it has set to meet its long-term needs, which this year is 675 million pounds.

Pensions consultants condemned the move, saying the scaling factor more than doubled from the PPF's original estimate of 1.6 made late last year.

The big hike between the preliminary estimate and the final figure makes it almost impossible for firms to estimate how much they must pay to the PPF each year, critics said.

But PPF Chief Executive Partha Dasgupta told Reuters the big increase reflected the fact that it had received much more detailed information of the financial strength of many schemes since the end of last year.

"We were very clear it was a provisional estimate and that we were expecting a lot of data to come in and that it could not be relied upon as the final determination of what the scaling factor should be," said Dasgupta.