Dailly has scored six goals in 65 games for Scotland

Dailly, 33, will be eligible to play for Saints in their Championship game against Barnsley on Saturday.

The Scottish international has been with West Ham since 2001 but has not played for them this season.

"Christian will give us the experience and composure we need at the back right now," Saints boss George Burley told his club's website.

"I am delighted to bring him to the club for an initial month and we will take it from there.

"Christian is a leader, a good character. He is enthusiastic and he is versatile.

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"The injuries to Claus Lundekvam and Darren Powell have made it difficult to find the right blend in the defensive line so bringing in Christian will give us a big boost.

"I watched him in the reserves recently and he did well. He is keen to come, he is still fit and still hungry to play."

Dailly began his career with Dundee United before moving to Derby and Blackburn and he has played a total of 191 games for the Hammers.