A senior Government supply has advised Express.co.uk that some ministers imagine Transport Secretary Mark Harper might use reserved powers to cease Sadiq Khan's hated ultra-low emission zone (ULEZ) to outer London.

The view is affirmation that there are splits throughout the Conservative Government over the way to sort out Mr Khan's plans to begin charging tons of of 1000's of drivers £12.50 a day from August 29.

But the issue inside Government is known to be Department for Transport officers who're strongly advising Mr Harper in opposition to making an attempt to step in over Mr Khan's new tax on drivers in outer London.

The briefing has come after Express.co.uk revealed the legal basis for the Tory Transport Secretary to stop Mr Khan's plans.

Mr Harper, nonetheless, has continued to insist there's nothing he can do as a result of the problem is devolved to the Labour London Mayor.

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One senior Government supply advised Express.co.uk: "The legal advice is that it's not clear cut. It depends on how you treat the environmental aspect.

"I'd assume they may step in however Department for Transport assume in any other case."

The source made it clear that some ministers believe Mr Harper should intervene and test the law in court if Mr Khan challenges it.

Tory MP Craig Mackinlay has quoted the 1999 legislation which created the position of an elected London Mayor and gave the scope of its powers and when ministers could overrule in the national interest.

He and around 40 Tory MPs have made it clear they believe Mr Harper can intervene too.

The Greater London Authority Act 1999 allowed interventions including when the Secretary of State considers that "a. the transport technique (or any a part of it) is inconsistent with nationwide insurance policies relating to move, and, b. the inconsistency is detrimental to any space exterior Greater London, he might direct the Mayor to make such revisions of the transport technique with a view to take away the inconsistency as could also be specified within the route".

The Bill adds: "Where the Secretary of State provides the Mayor a route below subsection (1) above, the Mayor shall revise the transport technique in accordance with the route."

Mr Mackinlay said: "In my view, given the significance of London to the nationwide economic system and transport, the Secretary of State ought to train powers to cease the anti-motorist campaign being pushed by this failed Mayor which is able to damage the poorest hardest and which moreover has financial repercussions throughout the South East and the broader nation."

But a source close to Mr Harper has insisted that "the authorized recommendation he has obtained" says he can not intervene.

The stress on the problem has mounted after a authorized problem by 5 Conservative-led councils in opposition to the Mayor's growth of ULEZ was dismissed final week.

It means petrol autos older than 2005 and diesel autos older than 2015 can be hit with day by day expenses of £12.50 per day as much as round £4,500 a yr.

Mr Khan is urgent forward with the scheme regardless of a public session popping out in opposition to the growth and Labour blaming his proposals for his or her defeat within the Uxbridge and South Ruislip by-election final month.