By this afternoon we will know if the coalition is going to financially deliver on its pledge to be the “greenest government ever”.

In delivering his Budget, George Osborne will today break his silence on the Green Investment Bank.

The Chancellor has given little away in recent months about the bank, to which he pledged £1bn in last year’s Comprehensive Spending Review.

In today’s Budget he is expected to increase this financial commitment to £2bn and say that it could raise funding worth £18m within four years.

But there are concerns that the Treasury seems to be setting a target of 2015 for the bank to actually begin lending. With the UK needing to invest £200bn in its low carbon economy by 2020, some feel this is leaving borrowing too late.

Earlier this month, the Environmental Audit Committee published a report into the bank, and its chair Joan Walley said: “If the government is serious about being the ‘greenest ever’, the chancellor must ensure the green investment bank can do what it says on the tin and raise extra capital like a real bank. The UK desperately needs a game-changing injection of private sector investment if we are going to meet our climate change targets and move to a green economy.”

And Greenpeace executive director John Sauven this week said that waiting until 2015 “throws into doubt Britain’s chances of building a low carbon economy and means we will now lose jobs and industries to places like China, Germany and Silicon Valley in California”.