Health minister Norman Lamb says he can no longer accept assurances from ambulance chiefs at face value after it emerged the trust had not met any of its emergency response targets in Norfolk, Suffolk and Cambridgeshire since April.

The North Norfolk MP was speaking as the East of England Ambulance Service Trust (EEAST) admitted to the EDP that extra ambulances introduced in Norfolk and Suffolk last Monday were still not running full time.

In every month of this financial year the trust failed to reach its eight-minute and 19-minute targets for responding to category A patients – those in a life-threatening condition.

Over 10 months from April 2012 to January 2013, the East of England Ambulance Service Trust (EEAST) failed to meet its target of responding to 95pc of calls within 19 minutes and 75pc of calls within eight minutes in the three counties.

Its worst performance over the 10 months was in Norfolk where just 64pc of eight-minute target calls were responded to within the time frame.

Mr Lamb admitted that he could no longer accept assurances at face value from ambulance chiefs.

'So many assurances I have been given have not been met,' he said.

Mr Lamb said the problem was two-fold – ambulance turnaround times at the Norfolk and Norwich University Hospital being too long and the high rate of sickness leave among staff.

He said: 'The sickness absence is the highest of any ambulance trust in the country. It is related to levels of morale and shows the pressure they are under.'

In Suffolk, 67pc of A8 calls were reached within eight minutes while the figure for Cambridgeshire was 68pc, well below the average for the trust and target of 75pc.

The 19-minute response times also made grim reading for the region, with the trust not meeting its targets in any of the 10 months in the three counties as well as in Great Yarmouth and Waveney.

It comes a week after the trust introduced 15 extra ambulances to its fleet following a review.

As reported in the EDP last Monday, none of the 15 ambulances was working full time due to a lack of staff willing to work overtime.

The trust said yesterday that they had made progress since last week with ambulances in Cromer, Diss, Potter Heigham and Beccles running 24-hour days but not for the whole week.

In Cromer, Potter Heigham and Beccles the ambulances are operating full time three days a week and in Diss one day.

The extra ambulances in Dereham, Downham Market and Mildenhall are still not running full time on any day of the week.

Suffolk MP and health minister Dan Poulter, who has pushed for improvements within the service, called the figures 'hugely disappointing' but 'unsurprising'.

The report, by the trust's director of strategy and business development, Adrian Matthews, will go before the service's board tomorrow.

It also said that patient handover delays at hospital continued to be a problem with the average waiting time remaining at 20 minutes for the last two months.

A spokeswoman for the service said: 'While recent patient surveys show the clinical care they receive is good, the ambulance service recognises the need to improve its performance against time targets and is implementing a number of measures to do so, including 200 new frontline recruits, 15 extra ambulances, which will be crewed by existing staff on overtime as much as possible until we get our new staff on board, better working with hospitals to tackle handover delays, more effective rotas and special cars to treat patients at home when they may not need to go to hospital.

'In addition our new chief executive Andrew Morgan is looking at other solutions and working towards a priority of meeting time targets.'

As well as 15 extra ambulances, the EEAST is also recruiting 75 new paramedics and 124 care assistants.