Taking part in the action are groups campaigning for immigrant rights, against racism, feminists and defenders of LGBT rights - all demanding a new nationality law that gives an unconditional right of citizenship to anyone born in Portugal.

At present Portuguese citizenship can be difficult to acquire for the children of immigrants whose situation is not legally recognised - even if those children were born in Portugal. Citizenship is only automatic if at least one of the applicant's parents has been legally resident in Portugal for at least five years.

The Communist Party bill would recognise citizenship for anyone born in Portugal so long as one of their parents - whether Portuguese or foreign - is resident in the country. The acquisition of nationality by naturalisation, meanwhile, would depend only on the length of the period of residence.

The Socialist bill would make more changes to the existing law, "aiming to maintain in the law criteria of granting of citizenship based both on 'jus soli' and on 'jus sanguinis' (lineage)". The party's argument is that Portugal is a "country simultaneously a country of emigration and of immigration" and so needs to reinforce the "legal protection and access to nationality of people who have chosen in Portugal to lead their lives working, starting a family, meeting their obligations and actively and positively contributing to the country's development."

As for children born in Portugal, the Socialist bill reduces the minimum required legal residence for one parent for eligibility, to two years.

As for the legal minimum required to seek naturalisation, it would be reduced by one year, to five.

In addition, minors could become Portuguese if they have concluded at least one basic or secondary school cycle in Portugal.

The Socialist bill also stipulates that "knowledge of the Portuguese language necessary for naturalisation is now presumed to exist for applicants who are natives and nationals of Portuguese-speaking countries."

In April the government approved a statute to allow the granting of citizenship to children born abroad who are the grandchildren of Portuguese citizens, so long as they have "real ties linking [them] to the national community", among other requirements.

President Marcelo Rebelo de Sousa symbolically promulgated the statute on Saturday, Portugal Dat.

Last year the number of requests for Portuguese citizenship reached a seven-year peak, at 35,416.