Mayor of London Sadiq Khan has been accused of providing "false and misleading" information over plans to extend ULEZ to the border with Kent.

The Labour leader has come under fire for the expansion plans, which would see drivers forced to fork out a £12.50 charge for using old and high-polluting vehicles when driving in all London boroughs, including between Bexley and Dartford.

After a 10-week consultation, it was decided on November 25 the ULEZ will expand in August this year, in a move the mayor claims is needed to tackle London's poor air quality.

Now Conservatives are accusing City Hall officials of trying to "manipulate" the consultation process, based on documents attained through freedom of information requests.

The confidential briefing document and minutes suggest the mayor was given a rundown of the consultation's findings on September 29.

However he denied knowledge of the findings at a session of mayor's question time at City Hall two weeks later on October 13.

The mayor's office said Mr Khan was not informed of the consultation process and only made decisions after considering the full final report from Transport for London (TfL), which he first saw on November 18.

The Tories also allege extra advertising and polling were paid for to boost support for the scheme, and thousands of responses from campaigners against the scheme were excluded.

More than halfway into the consultation, two-thirds of respondents opposed the expansion, and officials then spent thousands of pounds on digital marketing on Snapchat and Instagram, in a move the Tories say was designed to target young people, who are more likely to be concerned about air quality and climate change.

TfL also commissioned a survey by YouGov, which found that only 27% of respondents opposed the extended ULEZ.

And nearly 5,000 email responses opposed to the extension, organised by pro-motorist campaign group Fair Fuel, were deemed "copy and paste" and were excluded from the tally.

This reduced the opposition to the scheme from 67% to 59%.

A spokesman for the mayor said the consultation was not a referendum, and TfL made modifications to the scheme based on feedback received during the consultation, including addressing cost of living concerns with a £110m scrappage scheme for low-income Londoners, and extending the exemptions for disabled Londoners.

The spokesman continued: "The real scandal is that toxic air leads to the death of thousands of Londoners every year, which is why the Mayor took the difficult decision to expand the ULEZ London-wide.

TfL takes its responsibility to run robust and legally compliant consultations extremely seriously, with an independent consultancy putting together the final analysis and report, and any suggestion that TfL or the Mayor has sought to influence the results of the ULEZ consultation is simply untrue.

“As part of a rigorous consultation process, it was right for TfL to seek responses from as wide a range of Londoners as possible, including young Londoners – whose lives will be affected by air pollution for years to come.”

The spokesman added that all of the 58,000 consultation results were reviewed and analysed, besides 24 which were flagged as abusive or threatening and were therefore not processed in line with TfL's policies.

The most recent expansion in October slapped around 80,000 Kent motorists with an £80 fine after driving into the new ULEZ zones.

By area, Medway motorists were most frequently stung with 16,689 fines amassed, followed closely by Dartford (10,320) and Gravesham (7,602). You can check whether your vehicle is ULEZ compliant using TfL's checker here.

Last month, Dartford MP Gareth Johnson criticised the plans, saying: "I told the minister that Dartford is likely to be the hardest hit area, when this scheme is introduced next year, as the border straddles the local area and the scrappage scheme will only apply to Londoners.

"We also have no control over the London Mayor. Many of the poorest people in Dartford will suffer a huge financial burden if this goes ahead.”

Labour leaders in Kent have also voiced their discontent, with Gravesham council leader John Burder declaring he is "not a fan" of the new charging scheme.

The Tories on the London Assembly have now asked for an investigation by the GLA's monitoring officer who oversees alleged misconduct complaints.

Their transport spokesman Nick Rogers said: "We now have overwhelming evidence that Sadiq Khan has committed serious misconduct by violating the integrity of the consultation and improperly excluding thousands of legitimate responses.

"The mayor must now explain himself to Londoners, who participated in this consultation in good faith.

"The behaviour cannot stand and must be addressed by the appropriate authorities."