The family is in London tending to Mr. Sharif’s ailing wife, Kulsoom Nawaz Sharif. She has cancer and has been on a ventilator, according to officials with Mr. Sharif’s political party, Pakistan Muslim League-Nawaz. His request that the verdict be delayed for at least one week was rejected by the judge earlier on Friday.

Mr. Sharif, speaking to reporters in London late Friday, said he planned to return to Pakistan and was willing to go to prison in his effort to free Pakistanis “of the slavery imposed on them by some generals and judges,” He did not say when he would return.

Members of the Sharif family had said before the verdict that they would appeal any convictions, but they are unlikely to get relief from the higher courts.

The conviction also bars Maryam Sharif from contesting the July 25 elections, in a blow to Mr. Sharif’s ambitions for his daughter to play a leading role in national and party politics. Ms. Sharif has emerged in recent months as a powerful voice for civilian rule and against the military’s interference in politics.

Mr. Safdar, the son-in-law, is in Pakistan but was not in court when the verdict was announced. He is campaigning in his hometown of Mansehra in the country’s northwestern Khyber-Pakhtunkhwa Province and was expected to hold a news conference later on Friday.

Mr. Sharif and his daughter have said that they are not afraid to go to jail, but it remains to be seen whether they will return to Pakistan before the elections. Political opponents have already said that the Sharif family is in an unannounced exile.

Their absence is bound to further worsen the fortunes of their party, known by the abbreviation PML-N.