By Jonathan Stempel and Joseph Ax

NEW YORK (Reuters) - A recent U.S. Supreme Court decision may have tainted the corruption convictions of former New York Senate Majority Leader Dean Skelos and his son Adam, a Manhattan federal judge said on Thursday, allowing them to stay free on bail while they appeal.

U.S. District Judge Kimba Wood said the Supreme Court's June 27 overturning of former Virginia Governor Bob McDonnell's bribery convictions raised a "substantial question" about whether her instructions to the Skeloses' jury were proper. She also said Dean and Adam Skelos were not flight risks.

The Supreme Court had ruled that routine political activities such as arranging meetings or reaching out to public officials generally did not qualify as "official acts" that could form a basis for criminal corruption prosecutions.

In a court filing last month, the Skeloses said the broader definition that Wood used when instructing their jury last December may have "passed muster" at the time, but in retrospect may have caused them to be convicted based on legal conduct.

Robert Gage, a lawyer for Dean Skelos, declined to comment. Christopher Conniff, a lawyer for Adam Skelos, could not immediately be reached for comment.

U.S. Attorney Preet Bharara in Manhattan had opposed bail pending appeal. A spokeswoman for Bharara declined to comment on Wood's one-page order.

Dean Skelos and Adam Skelos were sentenced in May to a respective five and 6-1/2 years in prison, following their convictions on fraud and bribery charges.

Prosecutors had accused the elder Skelos, a Republican, of using his position as Senate majority leader to pressure three companies that wanted his support in the state legislature into providing work and money to his son.

Sheldon Silver, the former Democratic speaker of the State Assembly, has also cited McDonnell as he seeks to overturn his conviction and 12-year prison term in another corruption case.

A lawyer for Silver could not immediately be reached for comment.

The case is U.S. v. Skelos et al, U.S. District Court, Southern District of New York, No. 15-cr-00317.

(Reporting by Jonathan Stempel and Joseph Ax in New York; Editing by Tom Brown)