The organisation that represents police in Avon and Somerset has criticised Conservative plans to introduce directly elected police commissioners.
The Avon and Somerset Police Federation said replacing a police authority with a commissioner could lead to a force becoming politically biased.
Labour and the Liberal Democrats have also opposed the plans.
Bristol North West Tory candidate Charlotte Leslie said a directly accountable individual was needed.
Police authorities are independent bodies of local people whose job is to ensure its force is run efficiently and effectively.
'Error of judgement'
Ms Leslie said: "You need an individual who is directly accountable and has a direct incentive to make sure the reality and not just the statistics and targets are getting better.
"That's what an individual would do."
A spokesman for Avon and Somerset Police Federation said: "In reality this is a bad error of judgement that has been ill thought out.
"Although it could be seen as far-fetched, what would there be to stop extremism coming into this role? Without a doubt there will be some political allegiance."
Paul Harrod, the Liberal Democrats' candidate for the same seat, said his party wanted to see an elected police authority.
"There should be more scrutiny, with elected people.
We are saying lets reform the current system, have more elected people the same as councillors. Have a say in your own police force."
Sam Townend, Labour's candidate in the constituency, said the police authority should remain as it is.
"I would have thought the last thing that we need is to intervene like the other two parties want - a whole raft of new elected politicians with bureaucracy, no doubt allowances and all the rest of it."
The candidates so far for Bristol North West are Charlotte Leslie, Conservative; Paul Harrod, Liberal Democrats; Sam Townend, Labour; Alex Dunn, Green; Philippa Jones, UKIP and Ray Carr, English Democrats.