Image copyright HS2

The UK and China have held "preliminary discussions" over giving Beijing's state-owned railway firm a role in building the HS2 high-speed rail line.

However, government officials said no "concrete commitments" had been made.

China's state railway company said it could build the line in just five years and at a much lower cost, according to a letter seen by Building magazine.

But Conservative MP Tom Tugendhat warned letting CRCC build HS2 would be "extremely questionable".

It comes after Boris Johnson this week approved the controversial HS2 scheme.

This was despite an official review warning costs could reach over £100bn, against a budget of £62bn.

Under current plans, the final stretch of the line is not due to be completed until 2040 - although Mr Johnson has said he wants that brought forward to 2035.

However, Building magazine reported that the China Railway Construction Corporation (CRCC) had written to HS2 Ltd's chief executive last month, saying it could build the line by the middle of the decade, for a much reduced price tag.

Any move to give Beijing a further role in the UK's infrastructure would almost certainly prove controversial, after Mr Johnson reportedly incurred the wrath of US President Donald Trump - as well as upsetting many Tory MPs - with his decision to allow tech giant Huawei to supply equipment for the 5G mobile network.

However, British officials are said to be sceptical that it could operate in the same way in a democracy with property rights, protected landscapes and powerful lobbying groups.

Analysis

By Katy Austin, BBC business correspondent

An offer by an experienced railway builder to solve all of HS2's issues might sound tempting, but whether it is likely to be taken up is another question.

Preparation work is under way and the vast majority of contracts have already been allocated for the project's first phase linking London and Birmingham.

The letter from the China Railway Construction Corporation lacks detail on its plans.

So it is unclear how seriously the approach is being taken - or whether discussions progressed beyond CRCC's interest being acknowledged and them being informed of process.

Its letter claims it could bring advantages worth overcoming obstacles for. But the politics of allowing Chinese investment in further key UK infrastructure would not be straightforward.

Mr Tugendhat, who is chairman of the foreign affairs select committee, said the UK was in "dire need" of a strategy around its relationship with China.

Mr Tugendhat told BBC Radio 4's Today programme on Saturday: "Have we decided to take back control from Brussels only to hand it over to Beijing?"

He added that projects in China are often completed quickly "because they don't worry about such minor matters as planning consent or workers' rights".

Media playback is unsupported on your device Media caption HS2: Views from along the track

Mr Tugendhat is also sceptical of Mr Johnson's decision to let Huawei into the UK's 5G network, describing the Chinese tech giant's presence in the network as akin to letting a "fox in the hen house".

The CRCC letter, also been seen by the Financial Times, states: "We are certain that we can offer a cost that is significantly lower than the projections we have seen.

"The advantages are, in our opinion, too great to dismiss on the basis that there are obstacles to overcome.

"You will find that the Chinese way is to seek solutions, not linger on obstacles and difficulties."

CRCC has transformed China's transport system, building most of the country's 15,500-mile high-speed network.

Supporters of HS2 say it will improve transport times, increase capacity, create jobs and rebalance the UK's economy.

Once it is built, journeys will be shorter. London to Birmingham travel times will be cut from one hour, 21 minutes to 52 minutes, according to the Department for Transport.

And while it is being built, it is expected to create thousands of jobs and provide a stimulus to economic growth.

A Department for Transport official said: "The DfT is always keen to learn from the experience of others and to consider approaches that offer value for money to the taxpayer."