A Home Office minister who once warned MPs that Britain's most dangerous drivers were "serial potential killers" faced accusations of hypocrisy today after pleading guilty to using a mobile phone while driving.

Liam Byrne, the Immigration Minister, told Sutton Coldfield magistrates’ court that he was taking an important call on a deportation matter at the time that he was stopped in Birmingham on July 6. In a letter to the court, Mr Byrne admitted that he had committed an offence the Road Traffic Act and apologised for failing to pull over.

The 37-year-old MP for Birmingham Hodge Hill was fined £100 with £30 costs and a £15 victim surcharge. He was also given three points on his licence, taking his current total up to six.

Motorist safety groups criticised the minister for setting the wrong example to other road-users.

"The annoying thing is the implication that the minister’s phone call while driving was so important that he couldn’t pull over to take it," said a spokesman for the Institute of Advanced Motorists.

"That is totally unacceptable: everybody who has a mobile phone, a car and a job could try to claim that by way of mitigation. It is imperative that ministers lead by example. If this call was so important, it should never have taken place at the wheel of the car."

Mr Byrne's conviction for what is a criminal offence will come as a embarrassment to one of Labour's up-and-coming stars, not only because of his job at the Home Office - where he once had responsibility for the police - but also because he has campaigned for road safety since his arrival in Parliament.

He once told a parliamentary committee that the most dangerous drivers were "serial potential killers" and said he was "shocked" at the leniency of sentences handed down to them. Mr Byrne, 37, has spoken in the Commons of the need for more action to cut deaths and accidents on the roads, and in 2005 tabled a petition from constituents calling for tougher penalties for dangerous drivers.

He also sat on the parliamentary standing committee which shaped the 2006 Road Safety Act, which increased fixed penalty fines for driving while using a mobile from £30 to £60 and for the first time introduced penalty points for the offence.

Speaking in the committee in 2005, he said: "I was shocked as a new MP to hear example after example of drivers who had killed innocent people walking off with no more severe a penalty than six points on their licence and a £150 to £300 fine. The most dangerous drivers are serial potential killers."

Mr Byrne’s website lists safer roads among the eight priorities on his Action Plan for Hodge Hill, boasting of his campaign for tougher penalties for killer drivers and welcoming new measures "to raise driving standards and improve awareness on the roads through better education and training of drivers".

The Ministry of Justice announced this week that the number of motorists handed on-the-spot fines for using their mobile phones at the wheel has rocketed by 71 per cent. It said that 126,800 fixed penalty notices were issued for the offence by police in England and Wales in 2005, up nearly 53,000 on the previous year.

Making calls at the wheel, which became a crime almost four years ago, contributed to a 35-per cent rise in careless driving offences. There were 129,700 mobile phone-related cases in all, with the extra 2,900 offenders either taken to court or given a written warning.

And on Monday, a motorist was jailed for two years for causing the death of an 80-year-old pedestrian while using her mobile phone at the wheel of her 4x4. Mother-of-four Anne Foster-Chia, 44, denied she was using her phone at the time of the accident, but was convicted by a jury at Sheffield Crown Court of causing death by dangerous driving.

Cynthia Barlow, chairman of crash victims’ charity RoadPeace, said: "It’s the law that you should not use a mobile phone while driving and he knew perfectly well he should have stopped and pulled over while making a call and he did not.

"The law is just taking its course as it should. But I hope other people will use it as a reminder that you shouldn’t use a mobile phone while driving because many people still do."

This afternoon, Mr Byrne issued a statement saying: "Talking on a phone without a hands-free is wrong. I have apologised unreservedly to the court."

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