By Jason Douglas 

LONDON--A poll Saturday showed a narrow lead for pro-U.K. campaigners ahead of a vote Thursday on whether Scotland should become an independent country.

The poll, conducted by Survation for the pro-U.K. Better Together campaign, put support for maintaining the union at 47% and independence at 41%. The remainder of the 1,023 people polled were either undecided or refused to reveal their voting intention, Survation said.

Recent polls have shown a pickup in support among Scots for independence but most still put the pro-union "no" camp narrowly in the lead.

U.K. Prime Minister David Cameron this week urged Scots to reject independence, saying he would be "heartbroken" if the U.K. was broken up.

Businesses, which have largely avoided straying into such a sensitive political topic, this week also entered the fray. Lenders Royal Bank of Scotland Group PLC and Lloyds Banking Group PLC said they planned to move their legal headquarters to England in the event of a pro-independence "yes" vote.

Scottish National Party leader Alex Salmond says Scotland would be much better off if voters back independence and give Edinburgh full control of Scottish taxes and economic policy.

Write to Jason Douglas at jason.douglas@wsj.com

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