Mr Watson, pictured left, told the Birmingham Mail he favours calls for the government to refrain from changing the Act, after a consultation was launched by the Independent Commission on Freedom of Information into possible amendments to FoI.
The Mail has also launched its own campaign to save the Act from being weakened by the government-appoint commission.
Speaking to the newspaper ahead of its launch, Mr Watson said: “I associate the Labour Party wholeheartedly with this campaign.
“The Freedom of Information Act has held public institutions to account and if it is diluted it will mean taxpayers lose out.
“We will shortly be announcing a consultation to establish whether the FoI Act can be broadened and strengthened.
“It is one of the most important pieces of legislation that journalists have to hold the powerful to account.
“I hope people across the West Midlands will support his campaign.”
Last month Mr Watson told the Express & Star, Wolverhampton, he wants private companies providing public services to be made accountable to FoI laws, in the first interview he gave after being elected Labour’s number two.
The Independent Commission is to look at providing greater “protection” for internal discussions, which include Cabinet discussions and risk assessments by government and local authorities.
It will also examine the ministerial veto and whether anything should be done to limit the burden which local authorities are arguing the Act places on them.
Regional editors are being urged to write to MPs in their newspaper’s circulation areas to fight proposals to restrict the Act.
The News Media Association has already given its back to the “Hands Off FoI” campaign, stating the legislation is under “a grave threat”.