Portugal's Prime Minister António Costa threatened to resign if parliament approves giving teachers salary increases dating back more almost a decade.

After a long emergency meeting with key ministers, and talks with President Marcelo Rebelo de Sousa, Costa addressed the country Friday and said final approval of the payouts "will force the government to resign."

Costa said "it would be easy" for the government to resign "today" but added that it is important people "know the consequences the approval of this bill will have" and said voting in favor would constitute "an irreparable breach" with the country's economic plans. According to Finance Minister Mário Centeno, approving the measure could cost the country between €600 million and €800 million a year.

The prime minister said the bill would create an additional cost of at least €340 million between this year and next, a figure that could rise massively if the retroactive payments are also given to other public sector workers who experienced pay freezes. He said such expense would have to be offset by cuts to investment and public services.

The Socialist leader's ultimatum followed Thursday's approval by a parliamentary committee of returning teachers' salary increases that were not paid during the country's debt crisis. The vote was unexpectedly backed by opposition parties, including the Left Bloc, which together with the Communist Party (PCP) provides support for the Socialist government.

The committee backed the return of money owed covering a period of nine years, four months and two days that teachers have demanded since November 2017. The government wanted to return pay over a period of two years, nine months and 18 days to compensate teachers for having their pay frozen.

Teachers had their salary increases frozen from 2005 to 2007 and from 2011 to 2017. A final vote on the payouts will be taken on May 15, before the parliament is suspended for European election campaigning.

So far, Costa has been able to avoid rifts with the two hard-left parties that keep his minority government afloat. The arrangement — known as the Geringonça or "contraption" — between the parties is based on a balance between leftist demands for reversing austerity and making eurozone budget commitments. If that delicate balance is upset, it could trigger a political crisis. Portugal is scheduled to hold a general election in October.

"[José] Mourinho and [Pep] Guardiola discussed more tactics of their teams when they managed Real Madrid and Barcelona than those parties discussed education in Portugal together." — Portugal's Finance Minister Mário Centeno

But opposition parties including his leftist backers called out the prime minister and accused him of grandstanding over the pay issue.

Left Bloc leader Catarina Martins said "there are no signs of crisis" that justify the government's position. In a Facebook post, Martins said there seem to be "attempts to create an environment of political crisis. This environment is totally artificial."

"The government's blackmail ... will not work because we will continue to be consistent in fulfilling our commitments," the PCP's parliamentary leader João Oliveira told reporters.

Other opposition parties joined in.

"A prime minister who turns his back two weeks ahead of elections does not deserve to govern," said Assunção Cristas of the conservative People's Party.

The Social Democrats' (PSD) leader Rui Rio accused the government of" lying" and of staging a " theater coup."

Finance Minister Centeno hit back at the opposition's sudden united front, telling broadcaster Sic Noticias that "[José] Mourinho and [Pep] Guardiola discussed more tactics of their teams when they managed Real Madrid and Barcelona than those parties discussed education in Portugal together. They have nothing to do with each other."

Costa's big worry is that if the teachers get the money, then everybody should have it.

The General Confederation of Portuguese Workers' (CGTP) Secretary-General Arménio Carlos defended the parliamentary committee's decision and said such payments should be extended to all public sector workers.

"The same government that says it does not have the money to respond to commitments it has with public administration workers is the same government that has recently made available, without blinking, more than €1 billion to the New Bank, a private bank."

The president of the Association of Police Professionals (ASPP/PSP), Paulo Rodrigues, told Lusa news agency the government will have to apply "the principle of equality" and make payments to police officers for money owed during the pay freezes.

"If the government does not apply it to all, it is showing negative discrimination for the other sectors," said Rodrigues.

The head of the National Federation of Teachers' Union (Fenprof) Mário Nogueira said Costa's attitude is all about political games, and "another attempt to turn public opinion against teachers."