Police officers are leaving the Thames Valley force before they have even served two years, figures have revealed.

Home Office data showed that 29 officers who departed the force in 2006/7 - 10 per cent of total leavers - were relatively new recruits who had not yet completed two years in the job.

The Liberal Democrats, who published the figures, said they showed more needed to be done to keep officers in the service, which covers Oxfordshire.

Some areas appeared to have even greater difficulties keeping hold of new officers than the Thames Valley.

The worst affected force was Surrey, where 51 new recruits made up 27 per cent of departing officers.

Other badly affected forces included Bedfordshire, Cleveland and North Yorkshire.

The figures included dismissals, voluntary resignations, medical and other retirements, transfers and deaths.

Jeremy Browne, Liberal Democrat Home Affairs spokesman, said: "Early dropout rates reflect low levels of motivation. It is important to retain our expensively trained police officers.

"There are massive variations between forces which should concern the Home Secretary. Where retention is particularly problematic, there is a risk that the public will receive a diminished service, so this problem must be tackled."

But a Home Office spokesman said resignations accounted for 1.5 per cent of the total workforce and had been consistent over the last three years.

He said: "This has to be set against the background of an expansion in police officer numbers over the period when more than 25,300 new officers were recruited.

"You always expect some officers to leave in the first few years if they realise the job is not for them.

"With higher recruitment in the last few years, higher numbers of officers would be affected by this, even if the proportions remained the same."

The spokesman denied there was low morale in the force and said recruitment and retention of officers was "strong".

He said: "Forces report that they receive around six applicants for each police officer post on average.

"Retention of police officers is good in relation to other occupations - six per cent of leavers for the police compared with between 12 per cent and up to over 20 per cent in other sectors."