Timothy Bertelsen's employers at the Child Support Agency thought he was laid up at home with a back injury when they did not see him for four months.

In fact he was in jail after being caught driving while banned - but doctored a sick note to cover his absence.

After his release he returned to work at the CSA for another six months before his crimes were exposed.

Bertelsen, 43, of The Ridge, St Leonards, is now back behind bars after receiving a 12-month sentence for forging his sick note.

He had also lied when he originally applied for a job with the CSA, claiming he had a clean criminal record when he had been convicted of conning an insurance company.

At Hove Crown Court, Bertelsen admitted obtaining a pecuniary advantage by deception and forgery.

Rowan Jenkins, prosecuting, said Bertelsen filled out a CSA job application form on January 6 last year.

He claimed he had no previous convictions, despite having been given a suspended sentence in 2001 for paying cheques made out to bogus claimants into his own account while working for an insurance firm.

Bertelsen started the CSA job last April but was jailed for four months last July when found guilty of driving while disqualified.

Mr Jenkins said: "It was found that he had been given a sick note from his medical practitioner signing him off work.

"He altered the date on the note by writing over the doctor's handwriting."

The forgery came to light last January.

Nicola Biggs, defending, said: "He was desperate for work."