Controversy has erupted over the appointment of committed anti-vivisectionist Norman Baker as the Home Office minister responsible for approving animal experiments in Britain. The Liberal Democrat MP for Lewes, East Sussex, has in the past presented petitions at 10 Downing Street calling for an end to all such experiments.

The appointment was described as "very unfortunate" by one senior scientist. Others have expressed dismay that a man with Baker's record should be given the job of policing animal experiments at a time when scientists are using them in increasing numbers to develop new generations of drugs for conditions such as Alzheimer's, Parkinson's, cancer and other major ailments.

Scientists insist that new treatments for serious illnesses cannot be developed unless their safety and efficacy is tested on animals. Similarly, they argue that progress in understanding basic biology, which underpins the creation of new medicines, cannot be achieved without animal research. About 4.11m scientific experiments on animals took place in 2012, an increase of 317,200 on the previous year.

Baker is vehemently opposed to this trend and in 2009 was one of a group of campaigners who presented a petition at No 10 calling for an end to animal research and claimed that many experiments were "painful and futile". He added that it was "time for the government to get a grip on this issue and push for a practical road map towards eliminating animal testing".

Nor has Baker shown any change in attitude since taking office. Last week he told the Observer that he still wanted to see the day when animal experiments were no longer necessary.

"I believe we are heading towards that day," he said. "The Home Office is about to launch a document which will highlight ways to reduce numbers of animal experiments in this country and I fully endorse it. This is not going to be an immediate revolution, but I believe we are already making progress in finding substitutes for animal experiments. One day, those will lead to us being able to ban them. I believe that day is coming."

This view was denounced by the neurobiologist Professor Colin Blakemore, a former chief executive of the UK's Medical Research Council. He said: "Baker is raising false expectations if he says that the time is coming when we can think of banning animal experiments and still carry out important medical research. I don't know what basis he has for believing that. It is very unfortunate that he is starting out from this position. No one wants to carry out experiments on animals but it is an unavoidable fact that we need them if we are to develop new medicines and treatments that will save people's lives."

Baker's Home Office appointment has already provoked the fury of many Tories because the Lib Dem replaced his right-leaning party colleague Jeremy Browne in last month's reshuffle.

The home secretary, Theresa May, was said to have been dismayed by the replacement of Browne with Baker, who has previously courted controversy with his book The Strange Death of David Kelly, in which he suggested the government scientist could have been assassinated and his murder covered up.

Baker told reporters that his Home Office posting had been given the go-ahead by the deputy prime minister, Nick Clegg, to "make sure there is a liberal voice clearly heard in the Home Office".