According to Gazeta Prawna, apart from the expelling of diplomats, some other sanctions may be introduced against Moscow as soon as by the end of the day.
The newspaper specified that much would depend on the results of the ongoing EU Foreign Affairs Council, in which Polish Foreign Minister Jacek Czaputowicz is taking part.
Skripal and his daughter Yulia were found unconscious earlier in March on a bench at a shopping center in the UK city of Salisbury. Both of them remain in critical condition.
Reacting to the accident, UK Prime Minister Theresa May said that it was "highly likely" that Russia was responsible for the incident and later went on to announce a package of anti-Russia measures, including the expulsion of Russian diplomats from the country, and the suspension of bilateral contacts between London and Moscow.
The Russian Foreign Ministry refuted all the allegations and requested the UK Foreign Office to allow a joint investigation into the case.
On Saturday, Russia announced retaliatory measures against the United Kingdom, declaring 23 employees of the UK Embassy in Moscow personae non-gratae in response to London's move.