LONDON, Oct 18 (Reuters) - British security company G4S on Sunday recommended its investors reject the hostile takeover offer sent to shareholders by Canadian rival GardaWorld the previous day.

The offer document details a cash bid at 190 pence per share, unchanged from when GardaWorld announced its intentions on Sept. 14, prompting repeated rejections by G4S, one of the world's largest private security companies.

"The board recommends that shareholders reject the offer and take absolutely no action," G4S said in a statement.

G4S, which restructured its business after a series of setbacks in recent years, says the bid from its smaller rival significantly undervalues the company and its prospects.

Shares in G4S, which were trading at 145 pence before GardaWorld announced its interest, stood at 209 pence at Friday's close.

GardaWorld, majority owned by buyout firm BC Partners, said in its offer document that the cash bid would reward shareholders' "patience with a business that continues to face legacy challenges and future uncertainty".

"It is time to draw a line under G4S's past and give this company a brighter future," said GardaWorld founder and CEO Stephan Cretier.

G4S said early this month that U.S. rival Allied Universal had expressed interest in making a counter offer. (Reporting by Paul Sandle Editing by David Goodman)