Shadow Infrastructure Minister Lord Adonis has thrown his weight behind a campaign to bring the Thameslink line under the direct control of Transport for London.

The Labour peer also spoke of the need for step-free access at Mill Hill Broadway station during a visit to Hendon station with Labour’s parliamentary candidate for Hendon, Andrew Dismore, yesterday.

Lord Adonis said: “We are keen to see the substandard Thameslink service brought under the direct control of the Mayor. It’s just not good enough. The service is deteriorating, it needs to be made more accountable to Londoners.

“When the Mayor took over the north London line into the Overground, the service was completely transformed.”

The former Transport Secretary also said he was “keen to ensure” that a new station at the Brent Cross Cricklewood development – for which Chancellor George Osborne pledged money during last month’s budget – would not disrupt services at other nearby stations, such as Cricklewood or Hendon.

Speaking about Labour’s election campaign, he said: “The campaign is strong, but our watchwords are ‘no complacency’. We are not taking a single vote for granted. Everything depends upon campaigning activity by candidates. It will be won constituency by constituency.”

Asked about the way some Conservative candidates were using the SNP on their leaflets to warn people about voting Labour, Lord Adonis said: “It’s utterly ridiculous. The SNP is not on the ballot paper in London. They should be focusing on the issues that matter to Londoners.”

Andrew Dismore, who has been campaigning to bring Thameslink under the control of TfL, said: “Thameslink has become unreliable since the contract went to Govia in September. They haven’t got enough trains or drivers and it’s the same excuses all the time. It’s just not good enough.”

On the issue of step-free access at Mill Hill Broadway, the Labour candidate said: “It won’t be easy to provide. The Government supported huge cuts in the step free budget.”

In a statement, a spokesman for Thameslink said: “We are the right people to be in charge. We’re making improvements and have a new fleet of modern trains coming early next year – the first have already been built and are on the test track. In September we’ll introduce smartcard ticketing followed by a better timetable and, by 2018, 10,000 extra seats into central London.

“Punctuality on Thameslink is getting better as we follow up on our promised determination to tackle the issues we inherited when we took over the franchise in September. Our joint improvement plan with Network Rail and Southern is beginning to pay dividends with over 84.5 per cent of trains now arriving within five minutes of their scheduled arrival time and there is more to be done.

“There are more than 33 schemes worth £200 million to work on this and we have one of the biggest driver recruitment programmes under way in the UK. The big issue at the moment is the much-needed reconstruction of London Bridge, which has created a temporary bottleneck and we are making a series of timetable changes with Southern to improve reliability and ease congestion.”