* St. James’s Place, Barratt to join FTSE 100

* Tate & Lyle (LSE: TATE.L – news) , Amec (Other OTC: AMCBF – news) to slip to FTSE 250 index

* FTSE quarterly rebalance effective from March 24

By Atul Prakash

LONDON, March 5 (Reuters) – Wealth manager St. James’s Place and housebuilder Barratt Developments (LSE: BDEV.L – news) will be promoted to the blue-chip index of top British companies from the FTSE 250 index later this month, the FTSE Group said on Wednesday.

The two firms, whose market capitalisation has surged after a sharp share rally in the past months, will replace food ingredients company Tate & Lyle and engineering firm Amec in the FTSE 100 index. The changes will be effective from March 24, the group said in a statement.

A promotion to the top index can fuel further demand for a company’s shares from funds that track the FTSE 100 or use it as their benchmark, analysts said.

Newly independent St. James’s Place, freed from the strategic shackles of majority ownership by Lloyds Banking (Xetra: LLD.DE – news) Group, which sold out in late 2013, has impressed investors with its plans including the first acquisition.

That helped shares in the company, which manages money for wealthy individuals and families, rise 73 percent in 2013 and more than 30 percent since the Dec. 13 disposal by Lloyds to a lifetime high of 895.50 pence on Tuesday.

Around 9 percent of that performance has come since St. James’s said on Feb. 25 that it planned to buy Asia-focused Henley Group, an advisory business with around 400 million pounds under management and 4,000 expatriate clients in Hong Kong, Singapore and Shanghai.

Riding the property boom, Barratt Developments, Britain’s largest housebuilder by volume, has had a 27 percent share price rise this year on the top of a 68 percent spike in 2013, buoyed by the government’s “Help to Buy” scheme launched last year to free up lending to home buyers.

Barratt said in January its total home sales grew 71 percent in the first six months of its financial year compared to the prior year, driven by a recovery in Britain’s housing market across all regions.

British house prices are expected to rise 7 percent this year as a supply shortage and strong demand from overseas investors drive up the already-high prices of the London property market, a Reuters poll showed in February.

The elevation of St. James’s Place and Barratt to the FTSE meant that two other companies would leave to keep the total in the benchmark index at 100. Tate & Lyle and Amec will be leaving due to their relatively weaker share performance.

Under the quarterly FTSE review, any company rising to 90th place or above is automatically added to the FTSE 100 index, relegating the company at the bottom of the list to the mid-cap FTSE 250 index.

Shares in Tate & Lyle slipped 21 percent this year to touch their lowest in more than two years on Monday. The company, which sells sucralose under the Splenda brand and other ingredients to packaged food and drink makers, recently cut its profit outlook partly due to competition from cheaper rivals in China.

Amec, the other company that is leaving the FTSE 100 for the FTSE 250 index, has seen its shares gaining just 3 percent this year. The firm, which provides services and equipment for the oil and gas, mining, nuclear and renewable energy sectors, said this month it had been hit by weak prices and demand in Britain’s power market.

Small cap companies Just Retirement Group, Heritage Oil and Infinis Energy (Frankfurt: IF0.F – news) will find a place in the FTSE 250 index, by knocking down Edinburgh Dragon Trust , Devro (LSE: DVO.L – news) and Kenmare Resources (LSE: KMR.L – news) to the small cap index.