NEW YORK, NOV. 25 -- In its latest effort to expand into the financial services field, Home Shopping Network Inc., the leading shop-from-home television retailer, said today that it has purchased a regional brokerage firm and a seat on the New York Stock Exchange.

Joseph Connolly, chief financial officer of the Clearwater, Fla., company, said both purchases were part of the previously disclosed plans to offer financial services by mid-1988. Its best-known previous diversification effort fell through earlier this year when a deal to buy a Baltimore savings and loan institution was called off.

Connolly said the company bought the brokerage firm about three weeks ago, but he declined to identify it or to say how much it paid for the brokerage. He said the name and price would be disclosed later.

A Virginia discount brokerage, Brokers Securities Inc., announced today that it had held informal talks with Home Shopping about being acquired, but Connolly said that was not the brokerage.

He confirmed that Home Shopping had looked at Norfolk-based Brokers Securities, but said Home Shopping had "no interest whatsoever in it."

In late September, Home Shopping called off a proposed $40 million acquisition of Baltimore Federal Financial because banking laws appeared to prohibit marketing financial services from the thrift to Home Shopping's registered club members.

Connolly said Home Shopping paid about $750,000 for the seat on the New York Stock Exchange.

The NYSE said it was told a seat was traded Nov. 3 for $700,000 and that the highest price it knows of that was paid for a seat was $1.15 million on Sept. 21, about a month before the mid-October stock price collapse.

Connolly said Home Shopping wanted a seat on the NYSE to avoid brokerage fees and to have more control over transactions for its customers. He said the company might buy seats on other stock exchanges.

Home Shopping executives have said they hope to offer insurance, credit cards, stocks, bonds and mutual funds through the company's new financial service.

The company has not determined whether the financial services will be sold the same way it sells merchandise such as jewelry and furs, Connolly said, but the services will be advertised on Home Shopping's two television networks.

Home Shopping is the largest of the shop-from-home television retailers, operating two shopping networks 24 hours a day through broadcast and cable television outlets that can be seen by nearly 45 million homes.

For the fiscal year ended Aug. 31, Home Shopping reported an after-tax profit of $29.5 million on sales of $582.1 million.