Lech Walesa, the former leader of the banned Solidarity trade union, was told today by fiscal authorities he would have to pay a tax and fine equivalent to $2,700--about seven times the monthly salary he drew as the union's chairman--for a minibus his wife received as a gift from the West in 1981.

In an evident attempt to keep the union activist under pressure, Walesa and his wife Danuta were summoned to a tax office in the northern port city of Gdansk where they live and questioned separately for two hours about their personal finances.

A spokesman for the family said a summons for the interrogations had arrived last Monday, just after Walesa returned from a weekend visit to Warsaw, where he held his first known meeting with key members of Solidarity since his release from internment in November.

In recent days, Walesa has made clear he intends to take a tougher public line toward the government, which he said has refused to answer his appeals for a new dialogue.

Walesa said he would appeal the tax decision but noted there might be difficulty finding the appropriate documents because the records on the minibus had been kept by Solidarity's secretariat, which is now defunct.

Under further questioning, Walesa reported that he holds no foreign bank accounts and has a total of $770 in hard currency accounts in two Polish banks.