Proposals by the UK government for a new "bill of rights" have been rejected by the Scottish Human Rights Commission as regressive and unwelcome.

Professor Alan Miller, the commission's chair, said plans to replace the Human Rights Act with a bill of rights were an ill-disguised attack by UK ministers on civil liberties and an attempt to weaken existing legal protections for the vulnerable.

In his commission's formal submission to the panel investigating plans for a bill of rights , Miller said that the UK should instead keep the current act, and extend its range by incorporating all international human rights conventions into UK law.

Miller, a former director of the Scottish Council for Civil Liberties and recently appointed chair of the European group of national human rights institutions, said: "The current political climate concerning human rights, resulting in part from unsubstantiated attacks by UK government ministers on the Human Rights Act, means there are unfavourable conditions for a proper consultation on a UK bill of rights.

"Substituting a weaker bill of rights for the Human Rights Act is primarily intended to restrain our courts and make government less accountable to the public and to its international legal obligations.

"Especially in these times of budget cuts, the public – particularly the most vulnerable – need more and not less protection, and more and not less security in employment, housing, health, social care, and education."

The commission of inquiry, set up by the Ministry of Justice in March, is expected to produce its final report by late 2012.

The Scottish commission's criticisms partly reflect anxieties that a gulf is opening between the constituent parts of the UK on civil and political rights: voters in Scotland and Wales consistently vote for centre-left parties. The UK government's welfare reform programme has won little support in Scotland, where criticisms of human rights law come largely from the Scottish Conservative party.

Miller said the international conventions that ought to be included in the UK law included the UN conventions on the rights of the child and on the rights of people with disabilities, and the international covenant on economic, social and cultural rights.

He said the Scottish trend was to expand access to human rights through the devolved parliament's new "road map" to bring civil and human rights up to the highest international standards and establish a "living experience for all".

The Scottish government said it would publish its response to the bill of rights commission shortly, but a spokeswoman indicated it broadly supported Miller's stance, stressing that the Scottish model was to create an "inclusive" country.

"On the broad principles of human rights, the Scottish government is committed to creating a modern, inclusive Scotland which protects, respects and realises human rights," she said.

"Our vision is for a Scotland which plays its part as a full member of the European community of nations and that includes a commitment to the European convention on human rights."