The Nato alliance could disintegrate if European governments do not increase their spending on defence, an influential House of Commons committee is warning.

MPs on the defence select committee say the gap between US and European military capabilities must be narrowed.

Member states must be prepared to demonstrate in practical terms their continuing commitment to Nato's future

Bruce George Committee chairman

Nato could be undermined if member states fail to agree on a reform programme at a key summit in Prague later this year, according to the report.

Nato secretary-general Lord Robertson said the alliance faced a stark choice between modernising and being marginalised.

Lessons were being learnt, he stressed on BBC Radio 4's Today programme, and many European nations, including the UK and Norway were increasing their defence spending.

Lord Robertson said: "Unless the European countries are capable of investing in the capabilities which will allow them to work alongside the United States, then the United States will simply take decisions on its own."

Prague turning point

The MPs reject suggestions that the alliance is "dying".

But they say "robust decisions", including streamlining of Nato's structures, are needed to ensure its future as a viable organisation.

If European troops fall behind their US counterparts they may no longer be able to operate side by side, they warn.

The MPs say that by next year, US defence spending is set to be more than twice as much as the European allies put together.

Robertson says European nations know what is at stake

The report says: "Prague provides the opportunity for change and a failure to address the issues there could have serious and detrimental consequences for the future of Nato.

"We conclude that Nato must make real progress at Prague - if it does not, the imbalance will continue to grow and the bonds of inter-operability which hold together the US and its European allies will be broken."

The report acknowledges some "suspicion" in Europe over whether the US remains committed to the alliance and says those suspicions needed to be addressed.

US commitment?

On the other hand, the Europeans must also "pull their weight".

The Prague summit would test whether the allies now really were determined to improve their capabilities or whether the initiative was just a false dawn, said the MPs.

"If Nato is to remain a credible military organisation then we believe that all of its members must fulfil their commitments to improve capabilities.

The US was seen as sidelining Nato in Afghanistan

"This means having defence budgets which effectively deliver those capabilities."

Committee chairman, Labour MP Bruce George, said November's Prague summit would be a defining moment for the alliance.

Applications for membership from up to 10 former Soviet countries will be considered at the meeting.

Mr George added: "To meet these challenges member states must be prepared to demonstrate in practical terms their continuing commitment to Nato's future and the political will to take the hard decisions necessary to secure it.

"And they must do so in a way that convinces the United States that its interests continue to be best served by a strong and effective Nato."

Euro force

The committee also says the long-running dispute between Turkey and Greece over the use of Nato assets for the planned European rapid reaction force needs to be tackled.

Turkey - which is a Nato member but not in the EU - has blocked the use of Nato assets by the force because of differences with Greece.

The whole concept of the European Security and Defence Policy (ESDP) is under threat unless the row was resolved, says the committee.

"A question which needs to be answered during that time is whether the present impasse in fact demonstrates the unsoundness of the ESDP in principle," it said.

Conservative shadow defence secretary Bernard Jenkin said his party's doubts about the ESDP had now been echoed by the all-party committee.

"The ESDP is a thorn in the flesh, it is dividing Europe's attention when it should be concentrated on Nato as the primary alliance to provide for European security," Mr Jenkin told Today.