(Adds details, quotes, finance ministry reaction)

* Moody's cuts rating outlook to negative from stable

* Says cut in outlook caused by a rise in fiscal risks

* Shift to unpredictable policies impair investment climate

* Moody's Poland rating top among three major agencies

By Marcin Goettig

WARSAW, May 14 (Reuters) - Moody's Investor's Services cut the outlook on Poland's A2 rating on Saturday, citing rising fiscal risks and the new conservative government's shift to more unpredictable policies and legislation.

The move was expected by just over half the analysts polled by Reuters and follows Poland's shock downgrade in January by fellow rating agency Standard and Poor's (S&P) that sent the zloty to a multi-year lows.

"The first driver of the decision ... is related to the fiscal risks arising from a substantial increase in current expenditures ... as well as the government's intention to lower the retirement age," Moody's said.

Since coming to power in October, the eurosceptic Law and Justice (PiS) party has raised government spending by over 7 percent, passing a new child benefit programme worth about 1 percent of gross domestic product in 2016.

The program is financed mostly by a one-off source of budget revenue this year. The government says higher tax intake will help finance the programme in the coming years, but many economists remain sceptical about the plan.

Commenting on Moody's decision, the finance ministry said the government's long-term financial plan assumes the fiscal deficit at below three percent of GDP next year, subsequently falling to 1.3 percent by 2019.

INVESTMENT CLIMATE

Moody's also said the risk of a deterioration in the investment climate had increased due to the government's shift towards more unpredictable policies and legislation.

"(This is) reflected in the ambiguity with respect to the conversion of foreign-currency denominated mortgages and in the prolonged stalemate between the government and the country's constitutional court," Moody's said.

The PiS party has promised to help thousands of Poles who took out loans in Swiss francs when the franc was much cheaper than now. A team of aides to President Andrzej Duda, an ally of PiS, is working on proposals how to solve the problem.

PiS has also tried to reform the constitutional court in ways that critics say make it hard for judges to review, let alone challenge the ruling party's legislation.

Moody's said it could cut Poland's rating if the state's fiscal position or the investment climate worsen.

"A protracted (or escalation in the) conflict between the government and the constitutional court that leads to substantial capital outflows could also exert downward pressure on the rating," Moody's said.