The settlement afforded to over 145 deposed and retiring MPs after the general elections will cost the taxpayer £18m, the watchdog that regulates MPs' expenses has said.
The figure is based on the announced retirement of 87 MPs, including political heavyweights Gordon Brown and William Hague, and the expectation that 145 could fail to be re-elected, the Daily Telegraph reported.
The rout could be the biggest eviction of sitting MPs since Tony Blair's Labour won a landslide in the 1997 elections, which led to 160 sitting Conservative MPs losing their seats, according to the Independent Parliamentary Standards Authority (IPSA).
The number of ousted MPs is set to be high this year, because of the predicted collapse of Scottish Labour, which could lose as many as 40 seats the SNP.
The forecasts have been made by IPSA as part of its budgeting process for the next year.
Massive MP turnover
Speaking at a hearing in Parliament Marcial Boo, the chief executive of IPSA, told MPs: "We have made a number of prudent assumptions about the turnover of MPs in particular, based on past history, on the number of MPs – there are 87 – who have already declared they are standing down, and so on.
"We have assumed also that a further 145 seats will change hands on election night. That is a high estimate. We are not expecting that degree of change, but, for the purposes of our budgeting, we would rather be slightly more prudent than have to come back for a supplementary estimate if things become tight."
MPs who lose their seats in an election are entitled to claim "winding up" expenses for two months. This payment is up to £57,000 for MPs in London and £53,950 for those in the rest of the UK.
The money can be used to pay staff salaries, travel, remove office and second home furniture, and shred confidential papers, the Daily Telegraph reported.
They can also claim "resettlement payments" worth one month's salary for each year of service, upto six months – meaning experienced MPs will be in line for payments of up to £33,500.
In addition, IPSA expects the cost of redundancy payments for the staff of MPs standing down will be £2.1m, while those who are defeated will be £3m.