Ted Stevens, the longest-serving Republican senator in US history, was indicted today on criminal charges for concealing gifts he received from oil executives seeking to curry favour with him.

The indictment sent shock waves through Washington, where the 84-year-old Stevens is a legendary figure and Congress's strongest advocate for oil drilling in protected wilderness areas.

Stevens has been under investigation by the FBI for more than a year for his ties to Veco, an Alaskan oil company, and his delivery of $50m in US federal money to a non-profit group run by his former aide.

The senator was charged with seven counts of making false statements on government financial disclosure forms. Stevens "willfully engaged in a scheme to conceal" more than $250,000 in gifts he got from Veco, including furniture, vehicles and a barbecue grill.

"Stevens could and did use his official position on behalf of Veco" while receiving the gifts, according to the indictment. Prosecutors said the senator helped Veco win a $170m government contract for Arctic research as well as help with projects in Pakistan and Russia.

Seven Alaska state legislators - who dubbed themselves the Corrupt Bastards Club for their cosy relations with Veco - have been indicted in the government's probe of public corruption in Alaska.

The former chief executive of Veco, Bill Allen, pleaded guilty to bribery last year. Allen admitted to paying for a lavish remodelling of Stevens's house and giving the senator's son more than $240,000 in sham "consulting fees" to help secure favourable treatment.

Republicans already face an uphill battle in the November election, poised to lose as many as 40 seats in Congress as John McCain struggles to gain traction against Barack Obama.

Stevens's indictment makes matters worse for his party, as he is facing re-election and already trailing in the polls to Democratic opponent Mark Begich, the popular mayor of Anchorage, Alaska. The state has not sent a Democrat to Washington since 1974.

Political analysts were beginning to acknowledge this summer that Stevens, a fixture in Congress for 40 years, could lose to Begich. After federal prosecutors announced the indictment, some prognosticators questioned whether the man Alaskans still call Uncle Ted could lose to a little-known Republican foe in the party primary on August 26.

Stevens is famous through the US for his quest to unlock Alaska's Arctic National Wildlife Refuge to oil drilling. He fought for decades to lift government protections on the refuge, estimated to hold more than 6bn barrels of oil, but never surmounted Democratic opposition.

Stevens solidified his power during eight years in control of the Senate committee that sets federal spending. He remains adept at securing government money for his home state without public approval, a process known as "earmarking".

The Alaskan is also famous for his temper, often delivering tirades against critics while wearing a tie printed with the comic-book character known as Incredible Hulk.

Despite Stevens's irascible persona, Democrats and Republicans alike respect his experience and refrained from criticising him publicly today.

The senator's office in Washington was not responding to calls on the indictment.

Matthew Friedrich, assistant US attorney general, told reporters that Stevens would be allowed to turn himself in to authorities. He declined to comment on the possibility of a plea agreement that could spare the senator prison time.