* Panel gathering information, no decision on formal probe
* Chairman accuses S&P of "irresponsible" action
* House Majority Leader Cantor criticizes agency too (Adds details, quotes and byline)
WASHINGTON, Aug 8 (Reuters) - The U.S. Senate Banking committee has begun looking into last week's decision by Standard and Poor's to downgrade the U.S. credit rating, a committee aide told Reuters on Monday.
The aide said the panel was gathering information about the S&P move but no decision had been made on whether it will hold hearings into the downgrade.
While an official investigation has not been launched, the aide said that all options were being weighed.
Late on Friday, S&P said the world's largest economy no longer deserved the top AAA credit rating, cutting it one notch to AA-plus.
The move was driven by concerns over Washington's inability to achieve at least $4 trillion in long-term savings amid a national debt that has climbed above $14.3 trillion.
Instead, after a rancorous fight between Democrats and Republicans, Congress and President Barack Obama recently negotiated a 10-year deficit-reduction plan that could end up saving a little over $2 trillion.
Senate Banking Committee Chairman Tim Johnson, in a statement, called S&P's downgrade an "irresponsible move" that could have a far-reaching impact.
The Democrat said the downgrade may "have spillover effects that tax the American people by increasing interest rates on home loans, credit cards, and car loans, and by increasing the cost of finance for some state and local governments."
S&P also came under attack from House of Representatives Majority Leader Eric Cantor, a conservative Republican who has been outspoken in his opposition to tax increases.
In a memo to his fellow Republicans that was made public by his office, Cantor noted that S&P's analysis of the U.S. fiscal situation "is overly focused on resolving the debt crisis in a manner that would greatly worsen the jobs crisis."
He was referring to S&P's contention that "the majority of Republicans in Congress continue to resist any measure that would raise revenues" to help ease the country's fiscal problems.
During the debt limit negotiations, Cantor and fellow Republicans succesfully opposed raising taxes on Americans despite Democrats' insistence for more revenue.
Meanwhile, White House Spokesman Jay Carney told reporters that he was not aware of any administration conversations about clamping down on S&P and other ratings agencies through tougher regulations.
Since S&P's announcement last week, Republicans and Democrats in Congress mostly have been engaged in blaming each other for the government rating downgrade.
And with Congress having just started a month-long recess, legislative activity has mostly ground to a halt as senators and House members are scattered across the country.
One senior House Republican aide told Reuters that he had not heard of any new legislative efforts brewing on rating agency reform.
The House Financial Services oversight subcommittee, which held a hearing on the credit agencies last month, has no plans for another hearing, a congressional aide said late on Monday.
Columbia University law professor John Coffee said the fate of future reform efforts for the ratings agencies was uncertain.
Credit rating agencies were widely criticized for fueling the 2007-2009 financial crisis by assigning top ratings to securities that were backed by subprime mortgages, which then plummeted in value as the housing market collapsed.
The new Dodd-Frank regulatory reform law does not include a tough reform amendment offered by Democratic Senator Al Franken of Minnesota, but it did require a two-year study of the credit ratings industry, perceptions that it suffers from an inherent conflict of interest, and what to do about it.
Of particular concern is the fact that companies issuing financial instruments pay the ratings agencies to do the analysis that results in their ratings, Coffee said.
Governments do not solicit or pay credit agencies for ratings. (Additional reporting by Andrea Shalal-Esa and Sarah Lynch; Editing by Philip Barbara)