Senegal's lawmakers have passed a controversial constitutional reform that expands their powers while curbing those of the president, triggering protests outside parliament.

The reforms were passed by an overwhelming majority after heated exchanges in parliament, underscoring an escalating power struggle between President Bassirou Diomaye Faye and his former ally-turned-rival, parliamentary Speaker Ousmane Sonko.

The government said the reforms would be put to a national referendum, although no date has been announced.

Faye and Sonko came to power together in 2024 on the promise of sweeping reforms, but their alliance has recently fractured, fuelling political uncertainty in the country.

Relations between the president and his now-former prime minister deteriorated over several months, with Sonko openly criticising Faye for his handling of Senegal's debt problems.

It came to a head in May when Faye fired Sonko as prime minister, but Sonko, whose Pastef party has a majority of the seats in the National Assembly, was chosen by MPs as the parliamentary speaker.

The constitutional reforms, proposed by Pastef party, would strengthen parliamentary oversight by expanding lawmakers' investigative powers, requiring the government to disclose agreements about natural resources to parliament.

Other proposals include:

- The creation of a Constitutional Court to replace the current Constitutional Council - with nine instead of seven members

- Prohibiting a sitting president from serving as leader of a political party - a move seen as being aimed at President Faye, who remains a Pastef member but no longer holds an official party role. If enacted, it could make it harder for him to launch his own party ahead of the next election

- Barring a president signing into law certain acts during the period between a presidential election and the inauguration of the president-elect

- Expanding the powers of parliamentary committees.

Earlier on Monday, police fired tear gas to disperse scores of protesters outside parliament as lawmakers debated the constitutional amendments. Inside the chamber, tensions also ran high, with opposition MPs staging a walkout in protest.

Pastef, which has 130 of the National Assembly's 165 seats, said the changes were aimed at strengthening the separation of powers across Senegal's executive, legislature and judiciary.

But the opposition views the initiative as political revenge by the former prime minister, who retains significant influence over the parliamentary majority.

During Monday's parliamentary debate, Justice Minister Moussa Sarr announced the president's intention to submit the matter to a public vote through a referendum.

But Sonko questioned whether the president had the authority to do so, saying the reforms had been validly adopted with the backing of a majority of lawmakers.

The opposition and various civil society organisations have criticised the amendments and called for an immediate withdrawal of the bill.