Hungary's ruling party is set to push through changes to the constitution on Monday that critics say will curb democratic rights, despite warnings from European leaders and a protest by thousands of people in Budapest at the weekend, Reuters reported.

The changes are seen by critics as the latest in a series of moves by center-right Fidesz party to cement its position in public institutions via its large parliamentary majority.

They scrap all decisions by the country's top Constitutional Court made before the new constitution entered into force in 2012, discarding a body of law often used as reference.

They also create room for restrictive new regulations in higher education, homelessness, electoral law and family law - the main focus of Saturday's protest in the capital.

European leaders have warned they may run counter to European Union rules and civil groups planned a further protest on Monday evening to urge President Janos Ader to veto them.