German finance minister Wolfgang Schäuble has warned his cabinet colleagues not to expect any extras from a record budget surplus, with the cash earmarked instead for a record 3.6 million asylum seekers expected by 2020.

Days after Germany announced a €19.4 billion surplus, Dr Schäuble said refugee numbers would have to sink in coming months because Germany could handle no more.

Meanwhile, his deputy minister, Jens Spahn, added that Germany’s entire surplus is “by law completely reserved for financing the refugee crisis”.

“Money for other things that we might want is simply not there, even if the numbers look different at first sight,” said Mr Spahn to the Süddeutsche daily.

Given Dr Schäuble’s long-term commitment to a balanced budget, ballooning refugee spending has dashed ministries’ hopes of sharing in a budget surplus windfall.

German officials argued yesterday over the 3.6 million refugee forecast. It was published yesterday by the Süddeutsche, citing an internal economic ministry calculation. It is based on roughly half a million people arriving every year between 2016 and 2020, and added to the 1.1 million who arrived last year.

Germany’s migration chief said the figure was an “internal, purely technical estimate”.

“I’m not expecting these numbers,” said Frank-Jürgen Weise, head of the federal office for migration and refugees, adding that no one could give a reliable forecast of refugee numbers.

At the same time, Germany’s ruling grand coalition backed new measures in the Bundestag on Thursday to tighten asylum rules and reduce the influx of migrants.

One measure lowers hurdles for the expulsion of convicted foreigners, a hot-button issue after hundreds of women reported physical and sexual assaults in Cologne and other German cities on New Year’s Eve, mostly at the hands of migrant men.

With growing pressure on chancellor Angela Merkel to reduce asylum seeker numbers, the rule changes passed the Bundestag with a large majority of 429 votes to 147 against.

Another change will prevent refugees bringing their families to join them in Germany for two years after their asylum application is granted.

In addition the bill aims to speed up the asylum process, with special centres set up to deal with applications of so-called economic migrants from countries with little prospect of securing refugee status.

Berlin says the aim of the bill is to speed up their repatriation, freeing resources for refugees from war zones in urgent need of protection.

Rejecting the bill from the government benches was one member of Dr Merkel’s Christian Democratic Union (CDU) and 30 members of her junior Social Democratic Party (SPD).

Opposition Green leader Katrin Göring-Eckardt accusing the government of running scared from the hard-right Alternative für Deutschland (AfD) party.

The cap on family reunions was “irresponsible and shabby” politics that would “separate families”, she said.

“This is not measured, it is panic and chaos,” she said.

The opposition Left Party said the five-day race to get the bill through parliament was a reflection of a government anxious to deport people as quickly as possible.