Ryanair chief executive Michael O'Leary has called on Prime Minister Theresa May to take "radical" actions and approve new runways at three London airports.

Speaking in the capital on Wednesday (31 August), O'Leary urged May to give the green light to new runways at Heathrow, Gatwick and Stansted, insisting it was a necessary measure to solve the ongoing capacity issue that has beset airports in the south east of England.

O'Leary said a new runway at each of the three airports will "finally resolve the runway capacity issue for the next 50 years, while ensuring competition between airports delivers efficient facilities and prevents airlines and passengers being ripped off by gold-plated monopoly runways."

The government is yet to make a formal decision over which airport between Heathrow and Gatwick will be granted expansion permission.

He added the budget airline, which launched two new routes to Strasbourg and Faro from its London terminals, will slow its UK capacity growth from 15% this year to 6% in 2017 in response to the uncertainty triggered by the pro-Brexit vote.

O'Leary indicated the carrier would not base new aircraft in Britain in the wake of the outcome of the European Union referendum, claiming instead the group would have grown its UK operations by over 10% had Britain voted to remain in the EU.

Meanwhile, O'Leary added the airline will not be able to cut spending quickly enough, should ticket prices continue to fall this coming winter. A weakening pound and geopolitical instability in some of the most popular tourist destinations have put airlines under pressure in recent months.

The Ryanair CEO told reporters that while the airline had endured a successful summer, offsetting lower ticket prices with an increased number of passengers, it would struggle to lower spending even further, should ticket fares continue to fall.

"We're not yet revising the guidance," O'Leary said. "But we're very cautious on the full-year guidance. If winter fares fall by more than 10% or 12%, we will have to review."