Poland has said it will not allow the Organisation for Security and Co-operation in Europe to monitor its parliamentary elections next month.
PM Jaroslaw Kaczynski (L) may face a tight contest
The foreign ministry in Warsaw said Poland did not need observers because it was a well-established democracy.
The OSCE, which often sends monitors to cover polls in its member states, voiced surprise at Poland's move.
However, there are no fears that the 21 October elections will be rigged, our correspondent in Warsaw says.
The early elections were called by Polish President Lech Kaczynski after the parliament voted to dissolve itself earlier in September.
The ruling conservative coalition collapsed last month amid corruption allegations against the leader of a junior partner.
"The OSCE asked Poland to admit observers for the election but Poland rejected the proposal, underlining that Poland is a democracy," Polish Foreign ministry spokesman Robert Szaniawski said.
"It's a standard procedure that it is the country that invites OSCE observers for elections, so in this case OSCE made a faux pas," he added.
A spokeswoman for the OSCE poll monitoring group described the situation as "unusual".
"A monitoring mission has nothing to do with what we think of the state of democratic practices in a country," Urdur Gunnarsdottir was quoted as saying by Reuters news agency.
Poland is one of the 56 members of the OSCE, whose election monitoring headquarters are based in Warsaw.
As well as monitoring elections in undemocratic countries, the OSCE sends teams to nations likes France and the United States, the BBC's Adam Easton in Warsaw says.
Although Polish Prime Minister Jaroslaw Kaczynski has been accused of abusing the state's power, nobody seriously believes that his government is preparing to rig the polls, our correspondent says.
He adds that the government's refusal to co-operate has been widely criticised in Poland.
Some Western diplomats also say Russia could use Warsaw's example as an excuse to prevent observers from attending its elections later this year.