A £50billion new rail line between London and Birmingham could be held up by a year, a government watchdog has warned.

According to the The National Audit Office (NAO) the HS2 high-speed rail project is under financial strain and a predicted finish date of 2026 may not happen.

The NAO revealed that the Department for Transport (DfT) had asked HS2 Ltd, the company tasked with building the line, to assess what impact extending the timetable by up to a year would have.

The firm has also been called on by the DfT to review the schedule in the hopes of increasing confidence in completing the first phase on time from 60 per cent to 80 per cent, without raising the price.

Plans are 'on track'

Despite the revelation, the Transport Minister Robert Goodwill asserted that HS2 was "on track" despite the NAO warning the railway project was facing financial pressures.

Forecasts on the cost of the first phase of the project exceed available cash by £204 million, while phase two - taking the line to the north of England - contains some elements that are "currently unfunded", the report said.

The NAO report continued to warn the benefit-cost ratio of the scheme could fall from 1.7 to 1.5 if the programme was not delivered well within available funding.

HS2 would travel from Euston Station and through west London – including Northolt and Ruislip – to the West Midlands and beyond.

'A colossal impact'

Earlier this year Mr Goodwill heard from Ealing residents that the project would have 'a colossal impact'.

Talks of a HS2 tunnel under Hillingdon borough 'back on the table'

It also noted that, although significant progress had been made by the DfT and HS2 Ltd in the project - including some major procurements for phase one and processing 2,600 petitions - the timetable set by the Department was "too ambitious".

Head of the NAO Sir Amyas Morse said: "HS2 is a large, complex and ambitious programme which is facing cost and time pressures.

"The unrealistic timetable set for HS2 Ltd by the department means they are not as ready to deliver as they hoped to be at this point.

"The Department now needs to get the project working to a timescale that is achievable.”

'Under severe strain'

The chairman of the Commons Public Accounts Committee, Meg Hillier, added: "Today's NAO report shows that preparations to deliver High Speed 2 are under severe strain.

"The Department for Transport has, yet again, set unrealistic timetables for delivering this programme and HS2 Ltd is only 60 per cent confident that it will complete phase 1 by December 2026.

"The programme is at a critical juncture and the department has some major decisions to make if it is going to protect taxpayers' interests and deliver all that the government has promised from HS2."

But Mr Goodwill added: "HS2 is on track and the National Audit Office agrees.

"We have strong cross party support and are on schedule to gain the powers needed to start building HS2, which the NAO acknowledges is a significant achievement.

"We are on course to start construction next year and complete the scheme on time and budget."