Sir Paul Stephenson, the commissioner of the Metropolitan police, has privately lobbied the home secretary to make it harder for people to take legal action against his force, the Guardian has learned.

Critics say the plans amount to an attempt by the police to put themselves beyond the rule of law and undermine constitutional safeguards against abuses of power. The Met's chief says money is being wasted on speculative claims, with lawyers gaining large fees that would be better spent fighting crime.

The proposals are contained in appendices to a letter marked "confidential" and sent to Theresa May by Stephenson, who is Britain's most senior police officer, on 22 June. In the documents, released after inquiries by the Guardian, he suggests:

• Making it harder for people to sue the police for damages in civil actions. These usually involve allegations of brutality or wrongful arrest.

• Loading higher costs on to officers and other staff suing police forces at employment tribunals. These cases include claims of discrimination and unfair treatment.

• Charging the public a fee for freedom of information requests. The Freedom of Information Act is supposed to help citizens hold public bodies to account.

Last night, Stephenson's proposals were opposed by an alliance of human rights lawyers and civil liberties groups. The main body representing rank and file police officers attacked the employment tribunal plans. The government is considering various ideas to shake up policing, and the proposals are being considered by ministers and their officials.

Stephenson sets out a list of ideas to cut costs and free policing from what he sees as excessive bureaucracy. He says civil actions against his force generate money for lawyers, and drain police budgets.

He writes: "We believe there needs to be a radical shakeup of the system; currently for every pound paid out in compensation, up to £10 or sometimes more has to be paid out in legal costs to the claimants' lawyers.

"One of the key aspects is that the average settlements are well under £10,000 and most under £5,000, in other words these are not major areas of police misconduct with long-lasting consequences but often technical breaches."

Solicitor Louise Christian denounced the suggestion: "It's clearly an attempt by the police to escape the rule of law. When access to justice is denied, the principle of the rule of law is damaged. The rich and powerful can always go to court, it's people without means who can't."

James Welch, legal director of the civil rights group Liberty, said: "The ability to challenge police misconduct in court is a vital constitutional safeguard against abuse of power. Under current rules, if you lose a case in the civil courts you can expect to be ordered to pay your successful opponent's legal costs.

"A service bound to uphold the rule of law should not attempt to carve out an exception for itself."

Stephenson also writes that police are forced to waste money and time defending employment tribunal claims by officers or staff who then drop them, with no financial risk to the claimant: "As you will be aware, currently there are no cost disincentives for claimants lodging speculative employment tribunal claims which are withdrawn after considerable public resources have been expended in order to respond to such claims.

"We propose that a fee for issuing claims could be introduced and the grounds upon which costs can be made widened to meet these concerns."

Stephenson continues: "Similarly, there is currently no incentive for claimants to accept early offers of settlement and substantial cost could be saved if claimants were put on risk as to costs from the time that such an offer is made."

Paul McKeever, chief of the Police Federation of England and Wales, said: "I'm not aware of speculative claims being made. Going to an employment tribunal is the last resort people take after being frustrated by the system. Nobody wants to go to an employment tribunal – it's a horrible process to go through."

An employment solicitor, Makbool Javaid, who has defended the police against claims and has also sued forces, said: "You can bring a claim at an employment tribunal and it costs you nothing at all … Employers, not just the police, say it encourages a have-a-go culture."

Stephenson also urged that the home secretary introduce fees for freedom of information requests. In 2009-10 the force received 3,373 such requests, which it says takes time and personnel to process. The commissioner writes: "We welcome the recent government commitment to review the application of FOIA [Freedom of Information Act] and would encourage you to consider introducing a fee (as there is for Data Protection Act requests) to bring it into line with the Data Protection Act."

Releasing the documents, Scotland Yard declined to provide the commissioner's letter to May, but did release Stephenson's appendices to the letter, in which he set out his concerns and proposals.

Maurice Frankel, chair of the Campaign for Freedom of Information, said the plan would help police hide from scrutiny and cost the taxpayer more money: "The intention would be to discourage people making requests. The effect would be to shield the police from many of the requests they get."

A Met source said the government was considering Stephenson's proposals as part of its plan to reform policing in an era of cuts expected to be around 25%.

Last night, the Home Office said: The home secretary enjoys a good relationship with Sir Paul Stephenson. It is usual for him to write to her with his opinions and the home secretary always considers them carefully."

The Metropolitan police authority, which oversees the force, did not return calls for comment.