The UK should not abandon ambitious defence and foreign policies across the globe in the wake of conflicts like Afghanistan, Labour will say today.

But ministers have to be realistic about a rapidly changing world, the party will warn as it calls for a national debate on the role of UK Armed Forces across the world.

In a speech, the Labour's shadow defence secretary Vernon Coaker will say the UK's defence objectives are at a "crossroads" after the planned withdrawal of British troops from Afghanistan and deep military cuts.

His comments will be seen as a statement of intent after last summer's House of Commons vote on Syria. Earlier this month Tory MPs accused Labour of encouraging Russia's invasion of Ukraine with the vote on its ally Syria.

But Labour rejected as nonsense the claim that the party's decision not to back a Coalition motion on missile strikes could be viewed as appeasing Russia.

Ahead of the speech today to the defence think tank the Royal United Services, Mr Coaker said: "We are ambitious about the positive role that the UK Armed Forces and defence strategy can play in the world."

He said: "We are realistic in that we know we must strengthen and deepen our partnerships with existing allies, and seek to cultivate new ones, if we are to achieve our strategic objectives.

"With UK defence at a crossroad, the time is now right to consider what role we want our Forces to play in the world."