Improvements to the Northern and Jubilee lines have been "paused", with a dispute growing over the reasoning behind this.

Transport for London confirmed that they are temporarily pausing plans to buy more trains for the Jubilee and Northern lines as the investment and focus is moved to focus on capacity increases and the new Elizabeth line to open in 2019.

MP for Finchley and Golders Green, Mike Freer, said he is "disappointed but not surprised" over the delays, which he believes is due to a partial fare freeze put in place by Mayor Sadiq Khan, which he says has left a funding gap which could have been used on the Northern line.

Mr Freer said: "This delay is a direct result of Mayor Khan’s ill-judged policy. The Mayor was warned of the consequences, so this delay is disappointing but not surprising.

"My constituents that rely on the Northern Line to get to work know how much they’d have benefitted from increased capacity, particularly at rush hour."

However the Mayor's office has said there will be a new timetable in place in the New Year which will see 11,000 more people able to use the Northern line at peak evening times, and assures residents there has been significant investment with trains having been refurbished in 2015.

A spokesman for the Mayor of London said: "Sadiq is investing record amounts into the future of London’s transport infrastructure without burdening Londoners with huge fare hikes seen under the previous Mayor.

"This includes the biggest Tube capacity growth that London has ever seen.

"TfL’s modernisation programme and in-depth technical work means that they can increase the frequency of existing trains and improve the reliability and performance of the Northern line without the immediate need for new trains."

Chipping Barnet MP Theresa Villiers joined Mr Freer in opposing the decision not to buy more trains for the Northern line, saying she felt the upgrade of the line made  “real progress” under the Conservative Mayor, Boris Johnson.

She said: “Now Labour is back in power at City Hall, Mayor Khan has put the brakes on the project yet again. It’s back to the bad old days.

“This is further proof the Labour Mayors are all the same – they just don’t care about the suburbs.”

London Undergrounds Director for Strategy and Network Development, David Hughes, added: "Our modernisation programme and ?in-depth technical work by our new combined engineering division has improved performance and reliability.

"This means we can increase the frequency of our existing trains without the immediate need for new trains, making journeys quicker and more comfortable for thousands of customers every day."

Mr Freer said that Conservative candidate in the Mayoral election, Zac Goldsmith, along with Conservative GLA members, warned against the idea of freezing fares for fear that it would lead to a shortfall, and Mayor Khan's partial fare freeze, he says, will add up to a loss of £640 million over four years.

Labour GLA member and former MP for Hendon, Andrew Dismore, said with TfL's confirmation that frequency can be increased without new trains, there is no need to spend the extra money for the sake of it.

He said: "It is ridiculous to suggest spending such huge sums when not necessary; and in any event it shows the Conservatives' financial illiteracy, in that fares are revenue income whilst new trains would represent capital expenditure funded completely differently."

Further details on the changes to Northern line timetables will be made available in due course.