Incidents of passengers being stopped from entering London Underground stations due to overcrowding rose 3% in the past 12 months, new figures show.
There were 547 so-called "temporary station controls" from March 2015 to February 2016, according to data released by Transport for London (TfL) in response to a Freedom of Information (FoI) request by the Press Association.
This compares to 531 during the previous year.
More than a fifth of cases occurred at Oxford Circus, with 219 in the past two years.
TfL said it uses station control to "maintain a safe and reliable service".
There were 30 full station closures due to overcrowding over the two-year period. The figures do not include "business as usual crowd control".
Caroline Russell, Green Party Member of the London Assembly, warned that overcrowding on the Tube is "dangerous and causes delays".
London TravelWatch, a watchdog for the capital's transport users, claimed the statistics demonstrate the importance of investment in the network to boost capacity.
A spokesman for Sadiq Khan, Mayor of London, said: "Sadiq has been clear that we can't have a situation where people don't feel safe on the Tube, and TfL are already taking short-term measures to avoid overcrowding."
He called for a "more strategic approach" to tackle overcrowding in the long term, such as encouraging people to use other forms of public transport or to walk or cycle, pushing the Government to speed up the transfer of suburban rail services to TfL and supporting Crossrail 2.
Manuel Cortes, leader of the TSSA rail union, declared that the closure of hundreds of station ticket offices last year has exacerbated overcrowding in Tube stations.
He said: "Overstretched staff find it increasingly difficult to handle rush-hour crowds with the staff cuts forced through by the previous mayor, Boris Johnson.
"We believe the shutdowns and cuts are linked because the system cannot cope with the commuter overload coming into the capital every day.
"These figures should prompt an investigation into the increase in ticket office closures and how we are going to avoid them in the future."
TfL has previously said switching staff from ticket offices to ticket halls makes them more visible and effective.
Mick Cash, general secretary of the Rail, Maritime and Transport union, insisted that overcrowding is "a massive issue", adding that managing the risk of passengers falling in the gap between platforms and trains is "a daily problem".
TfL's website states that station control involves "temporarily preventing customers from entering the station because of crowding".
A statement released by TfL alongside its FoI response read: "(Station control) essentially means keeping the station open whilst managing the flow of customers to maintain a safe and reliable service.
"Temporary station controls normally last only a few minutes, and other entrances often remain available during that period for customers to use."
Between April 2014 and March 2015 more than 1.3 billion passenger journeys were made on the Tube.