Conservative leader David Cameron has apologised after being photographed ignoring red lights and cycling the wrong way up a one-way street.
Pictures in the Daily Mirror newspaper showed the politician breaching traffic rules as he cycled to work.
"I know it is important to obey traffic laws - but I have obviously made mistakes on this occasion and I am sorry," Mr Cameron said in a statement.
Campaigners criticised him though some blamed poor regulation and signage.
The Mirror followed Mr Cameron on three Wednesdays as he cycled to the Houses of Parliament from his Notting Hill home.
The newspaper featured Mr Cameron cycling the wrong way up a one-way street in Dawson Place, going through a red light in Great George Street, driving the wrong way around a bollard in the Mall and breaching a red light at the Houses of Parliament.
But the pictures merely highlighted the difficulties the average London cyclist faced, said cycling campaign group CTC.
"It shows what an ass cycling regulation [and] traffic management is in this country at the moment... we campaign in CTC for things like opening up one-way streets, which are allowed all over Europe," said director Kevin Mayne.
"[Mr Cameron] is a yard in front of the white line in front of the Houses of Parliament - frankly, that's where I'd go to get away from the cars, he was hardly jumping the light," he said.
He added that the story had also highlighted how difficult signage was for cyclists in London.
Cycling enthusiast and Tory candidate for London mayor, Boris Johnson, called for "zero tolerance" of cyclists who break the rules.
Speaking to ITV1, he said: "I am a militant cyclist myself and I love cycling and I want more people to cycle in London, but part of the deal has got to be that if we are going to expand cycling in London ... we cyclists have got to obey the laws of the road."
When asked to comment on his party leader's apparent breach of the rules, Mr Johnson said: "Show me the evidence."
Kevin Clinton, head of road safety for the Royal Society for the Prevention of Accidents, criticised Mr Cameron.
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I see far more dangerous driving by motorists than I do by cyclists.
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"It is essential that all road users, including cyclists, obey traffic laws. The laws are there for everybody's safety and, as always, it is disappointing when someone in the public eye sets a bad example," he said.
Road safety charity Brake stressed that all road users, including cyclists, needed to observe traffic rules.
"People are dying on the roads every day and we can't afford to become complacent," a spokeswoman said.
"As a role model, Mr Cameron must be aware that if he does break [the rules], it is going to send out the wrong message to those he hopes to inspire."
Steve Pound, Labour MP for Ealing North, said: "David Cameron aspires to make the laws of the land but can't uphold them."
The Tory leader, who has been keen to establish his green credentials, cycles to work once a week - usually on a Wednesday.
He found himself accused of hypocrisy in 2006 for cycling while being followed by a car carrying his briefcase, which he later said had only happened "once or twice".
Mr Pound added: "We all remember the last time [Mr Cameron] went the wrong way up a one-way street with a publicity stunt. At least this time his driver wasn't following with his shoes."
Dawson Place. Mr Cameron cycles the wrong way up a one-way street.
Great George Street. He cycles across a red light.
The Mall. He cycles the wrong way around a keep left bollard.
Parliament Square. He crosses the white line at a red light