A fresh strike by workers on Southern Railway was said to be "solidly supported" today, causing more travel misery for passengers.

The Rail, Maritime and Transport (RMT) union accused the company of mounting a "vicious campaign of lies and dirty tricks" after it claimed that conductors had defied previous stoppages.

Southern said more than 27 per cent of conductors turned up for work during strikes last week.

The two sides are locked in a bitter dispute over the role of conductors, with a series of strikes planned between now and December.

Union members will remain on strike for three days this week, forcing the cancellation of hundreds of services.

RMT general secretary Mick Cash said: "Despite a vicious campaign of company lies and dirty tricks, including the spreading of bogus numbers about staff working and an attempt to bribe our members with a £2,000 bounty to sell out on passenger safety, the strike action this morning remains absolutely solid.

"Passengers know that Southern Rail under GTR (Govia Thameslink Railway) is an unmitigated disaster, a fact confirmed by the all-party Transport Select Committee last week. They also know that the guards are fighting to put safety before private profit. That is the issue at the core of this dispute.

"The solution to this dispute can be achieved easily through a cast-iron guarantee of a second, safety-critical member of staff on all current services with a guard. If that safety guarantee is good enough for Scotland, it is good enough for the South of England."

Southern said first-class travel had been declassified across all its services, telling ticket holders they could claim back the difference.

Travel problems in south London were increased this morning by delays to Thameslink services due to defective trains and "congestion".