Scientists and engineers provide advice to ministers deciding on policy
The government is keeping scientists at "arm's length" and treating science as "a peripheral policy concern," a group of MPs has said.
The Innovation, Universities, Science and Skills committee says knowledge from experts is not being properly used to make informed policy decisions.
Instead of being sidelined, scientists should be able to communicate directly with the prime minister, it argues.
Former chief scientist Sir David King said reform was "critical".
A spokesman for the Department for Business, Innovation and Skills (BIS) rejected the accusation, arguing that science was fundamentally central to government operations.
The current chief scientific officer, Prof John Beddington, and his staff are part of the Government Office for Science (GO-Science).
Until two years ago, GO-Science lay within the Department of Trade and Industry, but was then re-housed to the Department for Innovation, Universities and Skills.
After another reorganisation, GO-Science has recently returned to the department responsible for industry - now (BIS).
The IUSS committee said that "shuffling the body responsible for providing cross-departmental science and engineering advice from one department to another" flew in the face of the government's stated aim of "putting science and engineering at the heart of policy".
"It reduces science and engineering advice to, at best, a peripheral policy concern, and, at worst, a political bargaining chip, " the report said.
Sir David told the BBC it was an "oddity" that the post of chief scientific adviser was relegated to a department rather than based in the Cabinet Office close to the prime minister.
"The state of knowledge developed by people in our institutes and universities on very complex matters is now quite remarkable, but there is a still a big gap between decision-making and the use of that knowledge base," he said.
"When I was in government, although I had a good relationship with both prime ministers I worked with, it was always a battle to get through the office into Number 10 and get that advice through when it was needed."
Committee chairman Phil Willis agreed that scientists must be given better access to ensure that policies are underpinned by sound evidence.
"Scientists are kept arm's length in some departments and they don't have access to the prime minister as clearly they need to do," he said.
Mr Willis said the government had "a good record" in funding scientific research.
"But it's how you use that science," he added.
Sir David King said he had to 'battle' to be heard by ministers
"For example, we've got a huge climate change agenda, we've got a huge energy agenda. Where are we using the scientific and engineering advice?
"Unless at the policy stage ministers are urged to ask that basic question, 'Where is the evidence to support our policy and if there isn't, how do we get it?'
"That makes good government."
The committee said that too often advisers came under intense pressure to agree with the government's stance on an issue.
They cited the case Prof David Nutt, chairman of the Advisory Council for the Misuse of Drugs, who was "hung out to dry" by ministers after claiming that recreational drug use was no more dangerous than horse-riding.
A BIS spokesperson said: "Science sits squarely at the heart of government and is key to helping Britain return to growth and build a stronger and more competitive economy. The chief scientific adviser reports directly to the Prime Minister and for the first time a science minister (Lord Drayson) now sits at Cabinet.
"This government has given an unprecedented level of commitment to science. We have committed to a ring fenced budget of record levels rising to £4bn by 2010/11 more than double what it was in 1997.
"Science is central to the work of the new Department for Business Innovation and Skills as evidenced by the central role it plays in policies to build Britain's future prosperity including a new £150m Innovation Fund to invest in high tech companies, a radical low carbon industrial strategy and a blueprint for life sciences."