BORIS Johnson looks set to back HS2 after Sajid Javid, the Chancellor, decided to throw his crucial weight behind the controversial rail project.

Whitehall sources suggested Mr Javid is now minded to support the high speed train initiative at a meeting with the Prime Minister and Grant Shapps, the Transport Secretary, today.

Having reviewed costs and alternatives the Chancellor will "broadly back" the high-speed line from London to Birmingham, Manchester and Leeds.

Mr Shapps has insisted that no decision on the controversial infrastructure project - the biggest in Europe - will be announced this week.

It has been estimated the scheme, which was allocated £56 billion in 2015, could cost up to £106 billion. It would be Europe’s largest infrastructure project.

At PMQs, the PM tantalised MPs when he told them a decision on the project would be made "very shortly".

He said: "I just want to reassure all of my honourable friends and everybody, whatever persuasion they may be about HS2 across this Chamber, that there will be an announcement and a decision very shortly."

Some £8 billion has already been spent on the scheme.

The meeting comes as Mr Javid, a Birmingham MP, has put pressure on Cabinet colleagues to identify where cuts of five per cent could be made in their departmental budgets.

In a letter, co-signed by Mr Johnson, the Chancellor urged ministers to identify projects that could be abandoned ahead of his first Budget in March.

The intervention was seen at Westminster as a bid to find resources to fund Tory election promises on infrastructure, health and law and order.

Whitehall's spending watchdog said this month that HS2 was over budget and behind schedule because its complexity and risks had been under-estimated.

The National Audit Office warned that it was impossible to "estimate with certainty what the final cost could be".

Phase One between London and Birmingham was due to open in 2026 but full services are now forecast to start between 2031 and 2036.

HS2 chiefs have insisted the rail project would cut rail times between Glasgow, Edinburgh and London significantly.

Business chiefs in the north of England have argued that pushing forward with HS2 is key to boosting transport links across the region and providing increased capacity on the overcrowded rail network.

Construction firms warn that scrapping it would cause major damage to the industry.

However, opponents insist HS2 is too expensive and the money would be better spent elsewhere, while several environmental groups say it would cause huge damage to natural habitats and ancient woodland.