CALGARY, Alberta, July 12 (Reuters) - Canadian energy infrastructure firm Inter Pipeline Ltd did not engage in any improper defensive tactics to fend off a hostile takeover bid from Brookfield Infrastructure Partners, the Alberta Securities Commission ruled on Monday.

Brookfield launched a hostile takeover bid for Inter in February, and last month revised its C$8.48 billion ($6.81 billion) buyout offer to include an all-cash option.

Inter modified its shareholder rights plan as part of a strategy to avoid the takeover and launched a strategic review looking for other suitors, which culminated in rival bidder Pembina Pipeline Corp making a competing C$8.3 billion all-stock proposal. Inter's board recommended that deal, which included a C$350 million break fee to shareholders.

Brookfield, whose offer expires on Tuesday, filed a complaint last month with the Alberta Securities Commission alleging Inter's tactics favored Pembina, but the regulator rejected the case.

"We were not satisfied that Inter Pipeline engaged in any improper defensive tactics," regulator Kari Horn said in Monday's oral ruling. ($1 = 1.2453 Canadian dollars) (Reporting by Nia Williams; Editing by Leslie Adler and Peter Cooney)