* Push for Trump impeachment increases political risk
* European stocks tumble, U.S. futures point lower
* Oil falls on worries about global economy
* Brexit chaos deepens, pound drops 1%: https://tmsnrt.rs/2l2BqTR
LONDON, Sept 25 (Reuters) - World stocks fell to a two-week low and risk assets withered on Wednesday after U.S. lawmakers called for an impeachment inquiry into President Donald Trump, raising the prospects of prolonged political uncertainty amid a fresh rise in trade tensions.
Adding to geopolitical tensions was heightened uncertainty over Britain's departure from the European Union after the Supreme Court ruled Prime Minister Boris Johnson had unlawfully suspended parliament. The pound fell about 1% in its biggest daily decline since the end of July.
The move by Democrats in the U.S. House of Representatives to impeach Trump has exacerbated market anxieties over global recession risks and the U.S.-China trade dispute. Trump delivered rebuked China for its trade practices in a speech on Tuesday.
MSCI's global stock index dropped 0.4% in a fourth straight day in the red - the longest losing streak since a rout at the end of July.
The pan-European STOXX 600 dropped 1.4%, led by technology stocks. France's CAC tumbled 1.5%; export-reliant Germany fell 1.2%.
"It is hard to imagine how long can the truce with China remain on trade and that is adding to the general cautious environment for stocks," said Neil Mellor at BNY Mellon in London. "As soon as markets start worrying about trade, they look at central banks for help, but there is increasing pushback from them, too."
The downturn in Europe followed declines in Asia. Tokyo's Nikkei suffered its largest loss in three weeks. China and Hong Kong dropped 1% or more.
China's offshore yuan weakened, many other emerging-market currencies weakened and oil futures extended their declines.
The downturn looked to continue in the United States, with U.S. stock futures indicating a 0.2% decline at open.
The impeachment inquiry and disappointing U.S. economic data had knocked Wall Street on Tuesday, sending the S&P 500 0.84% lower, its biggest daily decline in a month.
The U.S. House of Representatives will begin a formal impeachment inquiry over whether Trump sought help from the Ukraine to smear former Vice President Joe Biden, a front-runner for the 2020 Democratic presidential nomination.
It is unlikely that the inquiry will lead to Trump's removal from office. Even if the Democratic-controlled House voted to impeach Trump, he would then be tried in the Senate, where Republicans hold the majority and are unlikely to convict him.
"Despite the drama this process will inject into the rest of the Presidents first term, there is little justification for altering asset allocation now, unless one thinks that this issue is the decisive one that tips the U.S. economy into sub-trend growth and/or a profits recession," said JPMorgan's head of cross-asset fundamental strategy, John Normand.
Markets have already been roiled by political disquiet in Hong Kong from Britain to Italy and the Middle East, with the latest developments prompting investors to ditch riskier assets and flock back to safe havens.
The dollar index, measuring the U.S. currency against a basket of six other major currencies, nudged 0.3% higher. The safe-haven Swiss franc edged up 0.2% against the euro to 1.0845 francs.
Sterling dropped 1% to $1.2377, more than reversing its gains from Tuesday when Britain's Supreme Court ruled Johnson had unlawfully suspended parliament. Johnson vowed Britain would leave the EU by an Oct. 31 deadline come what may, but he now faces reinvigorated opposition to his plans. Britain's FTSE index dropped 0.8%.
"Predicting the ultimate outcome of Brexit remains difficult," said Mark Haefele, chief investment officer at UBS global wealth management. "As a result, the longer-term risk-return outlook for UK equities looks uncertain. We still advise being nimble on sterling."
The move to safe havens also saw euro zone government bond yields slip lower. Yields on sovereign debt across the bloc plunged this week, with many at their lowest since Sept. 12, when the European Central Bank announced a new wave of stimulus measures to boost economic growth and inflation.
The yield on benchmark 10-year Treasury notes stood at 1.6387%, the two-year yield at 1.6076%.
U.S. crude oil dipped to $56.19 a barrel. Brent crude dropped to $61.7 per barrel - both down nearly 2%.
(Reporting by Karin Strohecker, additional reporting by Saikat Chatterjee in London, Stanley White in Tokyo and Swati Pandey in Sydney; editing by Larry King)