ISTANBUL, Jan 19 (Reuters) - Turkey’s central bank left its main interest rate on hold at 7.5 percent for the 11th straight month on Tuesday, a widely expected move that could put more pressure on the languishing lira currency.

The lira has weakened sharply against the dollar since late December, when the bank shocked markets by leaving borrowing rates unchanged, a move that was widely seen as bowing to pressure from President Tayyip Erdogan, who has repeatedly railed against high rates.

Investors say the central bank is long overdue for a rate increase, both to rein in inflation - now hovering at more than 8 percent, far above an official target of 5 percent - and to put a floor under the lira, which has been hit by worries about political influence on monetary policy.

The bank held fire again, and also stuck to its overnight borrowing rate at 7.25 percent and its overnight lending rate at 10.75 percent.

A Reuters poll of 19 analysts this month found that all but one expected the bank to leave rates steady.

It also stayed mum on plans for policy “simplification”. The bank, which uses a complex system of multiple rates, last month said it would start to simplify policy once market conditions were stable enough. Investors have been waiting for any new signals the bank could move toward a more orthodox system of using a single interest rate.

The bank had previously hinted that it would raise rates in tandem with the U.S. Federal Reserve. Hot on the heels of a Fed hike last month, Turkey was also seen as raising rates in December. When that rate hike failed to materialise, investor concerns only worsened.

Earlier this month the lira broke through 3.0 to the dollar for the first time since October, and has remained stubbornly above the symbolic threshold since, weighed down by global market fears. (Reporting by Nevzat Devranoglu and Daren Butler; Writing by David Dolan; Editing by Jeremy Gaunt/Nick Tattersall)