ALEX Salmond's "obsession" with securing independence within 18 months of a Yes vote is unachievable and would mean Scotland would temporarily be locked out of the European Union, MPs warned today.

And members of the House of Commons Scottish Affairs Committee claimed that by leaving the UK "and thus the EU", an independent Scotland would give up a raft of benefits like its £300m annual share of the UK's multi-billion-pound rebate.

Not only that but, they pointed out, an independent Scotland would have to contribute to the UK's rebate; this, together with the loss of its share of the EU rebate, would cost each Scottish household an extra £900 over the budgetary period.

But Fiona Hyslop, the Scottish Government's External Affairs Secretary, dismissed the MPs' report, saying it simply reflected the Committee's anti-independence position and looked "particularly foolish" after it came on the same day it "became crystal clear that the threat to Scotland's membership is Westminster's reaction to the rise of Ukip and the Prime Minister's promise of an in/out referendum."

Launching the report, Ian Davidson, the Committee's Labour Chairman, said the Scottish Government had "drastically under-estimated the time, complexity and cost of negotiating a new position in the EU as well as the factors weighted against Scotland" in any membership negotiations. The Glasgow MP conceded that while it was likely an independent Scotland's application to join the EU would be accepted, this would not be done on either the timescale or the terms it would want.

"It is simply not credible that the Scottish Government would achieve the terms of entry that it seeks and especially not from the weakened position of its self-imposed deadline," argued Mr Davidson. "The people of Scotland deserve to be told the truth about the costs and difficulties or re-joining the EU if Scotland votes to leave the UK and thus the EU."

Among the benefits the MPs claimed an independent Scotland would lose, are:

l the Budget rebate, the loss of which would cost each Scottish household around £900 over the Budget period;

l the opt out on joining the euro;

l the opt out on VAT charges on food, children's clothes, books and newspapers and

l the loss of valuable EU structural funds currently redirected to Scotland through the UK.

The Committee said: "An obsession with securing membership of the European Union by a specific date has significantly weakened the Scottish Government's negotiating position.

It pointed out how some negotiations with the EU, such as on the Schengen travel area, would be dependent on an agreement with the UK on "mutually acceptable immigration policies, thus affecting the timetable".

But Ms Hyslop hit back, saying the UK's own legal expert had described the Scottish Government's 18-month timetable as "realistic" and she said Labour's most senior MEP had accepted Scotland "could maintain a position outside the of both the euro and Schengen".