NHS director of planning Alasdair Liddell has resigned to join a new Internet company specialising in communications between government and business.

Mr Liddell will leave tomorrow to become director of government services at iMPACT, a company aiming to handle 'communications between government and the citizen and government and business'.

A spokesperson for the Department of Health said that under civil service rules, Mr Liddell will not be allowed to work on projects involving the NHS for six months.

The move comes just three months after NHS chief executive Sir Alan Langlands announced his decision to quit, prompting speculation that this could mean a 're-structuring' of the NHS board to reflect the government's modernisation agenda.

Mr Liddell was one of several possible contenders to step into Sir Alan's shoes. A member of the NHS Executive board since 1994, he was widely credited with much of the work behind the New NHS white paper.

He was also in charge of the implementation of the DoH's information technology strategy.

The DoH said that while Mr Liddell would be leaving within days of his resignation being publicly announced, 'this move had been under negotiation for some time'.

This was why Mr Liddell had not been 'directly involved' in discussions about the 'national plan' for health due in July.

From next week, Mr Liddell's role will be shared between permanent secretary Chris Kelly and director of operations Ron Kerr.

NHS director of finance Colin Reeves paid tribute to Mr Liddell's 'knowledge, strategic orientation and organisational ability', which was 'invaluable' in his NHS career.

'He is very very organised. That was particularly exemplified by the way he has written up the minutes for board meetings . . . I think that was something that Alan [Langlands] very much appreciated.'

Mr Reeves added: 'He has spent quite a long time in a high-profile job.

I think both he and Alan will have felt that there comes a time when [the NHS] needs someone with a new outlook. I think everybody is aware that one day they have a sell-by date.'

Ken Jarrold, chief executive of Country Durham health authority and NHS director of human resources from 1994 to 1997 said Mr Liddell would be remembered for his 'intellectual rigour' in planning and work on communications.

Alasdair Liddell: over and out Mr Liddell, now 51, joined the NHS in 1972 and was district general manager of Bloomsbury HA from 1985-88 before becoming regional general manager of East Anglian regional health authority. In 1994 he was appointed director of planning for the NHS Executive.