June 24 (Reuters) - Lone Star Global on Thursday backed out from trying to take over Britain's Senior Plc (SNR.L) after the aircraft and car parts supplier this week rejected the private equity firm's fifth and final proposal.

London-listed Senior Plc said on Tuesday there was no basis for it to engage with Lone Star after the fund a day earlier said its 200-pence-per-share offer could only be increased if a rival suitor emerged.

Senior Plc has rejected all the five proposals from U.S.-based Lone Star, saying that they undervalue it. Shares of the company, which said trading in the five months to May was ahead of management expectations, are up about 70% so far this year.

Lone Star had until June 25 to make a firm offer or walk away.

According to British takeover rules, Lone Star could still return within six months, as long as some conditions are met, such as an agreement with Senior Plc's board and if the country's panel on takeovers and mergers intervenes, the fund said.

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