Train services in the South East have suffered more disruption, hours before rail bosses face a grilling from MPs.
Some passengers using Southern abandoned their journeys, while others reported being up to two hours late.
The operator said services between Brighton and Three Bridges were expected to be delayed until 1pm due to signalling problems at Balcombe in West Sussex.
Gatwick Express trains were also subject to 45-minute delays and short-notice cancellations because of the same issue.
Figures from the Office of Rail and Road (ORR) show the number of Southern services cancelled has risen from one in 40 in 2010/11 to one in 20 in 2014/15.
Representatives from Govia Thameslink Railway (GTR) - the company responsible for the Southern franchise - and Network Rail are being questioned at Parliament.
Rail Minister Claire Perry and several MPs whose constituencies are served by the operators will attend the private meeting, including Labour's Chuka Umunna and Conservatives Maria Caulfield and Huw Merriman.
They have voiced criticism over ongoing problems, including delayed services, engineering work and not enough carriages or train drivers.
A GTR spokesman said: "We know the train service has not been good enough and apologise to passengers. We are looking forward to meeting with the minister, listening to the MPs and explaining what we are doing together to improve the service."
Mr Umunna, MP for Streatham, told the Press Association: "They have been providing utterly appalling services for many months."
He added: "Usually what we have is Southern Rail and Network Rail seeking to blame each other when both are at fault.
"Southern Rail, by their own admission, don't have enough decent trains and did not recruit enough drivers.
"Network Rail continually mismanage engineering works which are often delayed and overrun."
Many passengers disrupted by Monday's problems took to social media to express their anger.
Jane Perry posted on Twitter: "Notices of refunds no help to people around me seriously worried about losing their jobs. Not good enough."
Adam Young said he had decided to "abandon ship and return home", while Arjo Ghosh joked: "We're only running two hours late!"
In December, Network Rail agreed to set up a £4.1 million reparation fund instead of paying a £2 million fine over the chaos at London Bridge station, which the ORR said would directly benefit GTR services - Thameslink, Southern and Gatwick Express.
GTR is also working on a remedial plan with the Department of Transport which would see financial sanctions imposed "in extreme cases".
Southeastern handed out coffee vouchers to passengers arriving at London's Victoria station and apologised for recent disruptions.
More than 10,000 people have signed a petition calling for the operator to lose its franchise.