The Government's spending on the armed forces has come under heavy fire from a string of former service chiefs in the House of Lords.

Admiral Lord West of Spithead said defence was 'in crisis', General Lord Dannatt said the country looked 'weak' and Admiral Lord Boyce warned the Government was 'seriously imperilling' the United States' confidence in the UK.

Marshal of the RAF Lord Craig of Radley warned the UK lacked the strength in numbers to fightback against a 'counterpunch' from enemy forces as 'nothing was left in reserve'.

The service chiefs were joined by peers from across the Lords including a raft of Tory backbenchers who urged ministers to commit to meeting the Nato target of spending 2% of national income.

Lord Dannatt, a former head of the army and independent crossbench peer, said the Government was showing a 'steadfast resistance' to committing to the target.

In a debate on defence expenditure, he said: 'I don't think I'm alone in being genuinely concerned that our new Government is not showing sufficient commitment to the security of our country or its citizens at home and abroad.'

He said it wasn't 'good enough' to say all the issues would be dealt with in the forthcoming strategic defence and security review (SDSR).

'Is President Putin going to wait until our SDSR is completed before he decides his next move in Eastern Ukraine or the Baltic?' he demanded.

'The dangers of another six months of prevarication is that the UK's position in the world will continue to look weak.

'The US will remain anxious that a once reliable partner is enfeebled and other European states who look to the UK for a lead on defence matters will indeed follow our limp lead and kick the issue of defence funding into the long grass.'

Lord Boyce, a former chief of the defence staff, said the 2010 SDSR had 'fundamentally weakened' the armed forces.

He said a close look at the figures showed the country had already dropped below the 2% target and he had 'no doubt further fudging' would take place.

'This SDSR looks like being a thinly disguised cuts exercise, which will emerge with no strongly thought-through strategic vision or recognition of such threat as those posed by Russia,' he warned.

'It seems we are on track to reinforce the perception round the world that we are a has been, we are no longer a serious player - especially by the United States.

'We should be particularly alarmed by the latter - a huge unquantifiable amount comes our way in defence terms underpinned by their confidence in our capability. We are seriously imperilling this.'