Transport for London (TfL) will investigate the impact of pay-as-you-go train fare hikes after some passengers saw prices rise by 38 per cent.

The off-peak cap for travelling between outer boroughs and central London was raised in November, meaning passengers in Zone 6 could be charged £11.70, up from £8.50.

That includes Surbiton, the borough's busiest station, where more than 4.6m journeys began last year.

At the time TfL's director of customer experience, Shashi Verma, said: "A cap is a cap, it is not a fare, and if you increase the cap it doesn’t mean people end up paying the value of the higher cap.

"In any major reorganisation of this kind, it always leaves winners and losers."

Conservatives said the change would benefit part-time workers who would no longer have to wait until 9.30am to travel, but Liberal Democrats warned of greater congestion during peak times.

Now TfL is to review the effect of price changes, according to John Biggs, Labour chairman of the London Assembly's budget committee.

Its review will be published in six months' time.

He said: "We don’t want to see outer London commuters being unfairly targeted to help fund this policy, particularly if it means more people packing onto peak time services."

"Supporting part-time workers is important, but the Mayor needs to be clear on the details of who’s being affected to pay for this.

"The Mayor should also look at the impact of increases to group fares - this could have a real impact on kids making school trips to museums and galleries."

Last week saw a call by Lord Adonis for suburban train lines to be incorporated into the London Overground system.

He said the move would improve "bleak" stations with better maintenance, more staff and more frequent trains.